ABSTRACT

THE EFFECTIVENESS OF VOCAL FUNCTION EXERCISES (VFES) ON VOCAL MEASURES WITH HEALTHY ADULT MALE

TRAINED SINGERS

Dr. Joseph Stemple created Vocal Function Exercises (VFEs) to help strengthen

and stabilize the vocal musculature. The exercises were designed as a therapy technique

to assist those with voice disorders. There is little research on the study of VFEs in

normal healthy individuals and even less research on the effects of VFEs on healthy adult

trained singers. Trained singers have the technical foundation to perform VFEs properly

and could possibly benefit and improve upon their strength and muscle tone due to their

established skills. The purpose of this study is to determine if Dr. Stemple’s VFEs are a

technique that could be used by healthy adult male trained singers to increase their

maximum phonation frequency range and maximum phonation time, and to decrease

jitter and shimmer. The study consisted of 3 male participants who were healthy adult

trained singers from the Fresno State Music Department who were enrolled in voice

lessons with a professor from the Music Department. The study utilized a single-subject,

multiple baseline across participants research design. The study consisted of baseline,

treatment, and maintenance phases. During the treatment phase, participants were

required to perform VFEs at home twice a day, two times each, and to meet with the

researcher once a week for probe measurements. The results from this study are

anticipated to enhance the vocal quality of established trained singers.

Maelyn Danielle De Fede December 2018

THE EFFECTIVENESS OF VOCAL FUNCTION EXERCISES (VFES)

ON VOCAL MEASURES WITH HEALTHY ADULT MALE

TRAINED SINGERS

by

Maelyn Danielle De Fede

A thesis

submitted in partial

fulfillment of the requirements for the degree of

Master of Arts in Communicative Disorders

in the College of Health and Human Services

California State University, Fresno

December 2018

APPROVED

For the Department of Communicative Sciences and Deaf Studies:

We, the undersigned, certify that the thesis of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the master's degree. Maelyn Danielle De Fede

Thesis Author

Fran Pomaville (Chair) Communicative Sciences and Deaf Studies

Don Freed Communicative Sciences and Deaf Studies

Anthony Radford Music

Ericka Olsen Communicative Sciences and Deaf Studies

For the University Graduate Committee:

Dean, Division of Graduate Studies

AUTHORIZATION FOR REPRODUCTION

OF MASTER’S THESIS

X I grant permission for the reproduction of this thesis in part or in its

entirety without further authorization from me, on the condition that

the person or agency requesting reproduction absorbs the cost and

provides proper acknowledgment of authorship.

Permission to reproduce this thesis in part or in its entirety must be

obtained from me.

Signature of thesis author:

ACKNOWLEDGMENTS

I am forever grateful to many incredible people in my life who have supported me

throughout my life and in accomplishing this thesis. First, I would like to thank my

parents, my sister, Bryna, and Michael. I cannot thank you enough for everything you all

have done for me, especially in completing the speech-language pathology graduate

program. Thank you for being there for me through all the excitement and stresses. I love

you all very much!

Second, I would like to thank my thesis committee chair, Dr. Fran Pomaville.

Thank you for your countless hours of work you put into this thesis. Your support and

guidance throughout my undergraduate and graduate career does not go unnoticed. I am

very lucky to have met you and worked with you on this thesis. Thank you for being an

amazing mentor and always encouraging me throughout my education here at Fresno

State.

Additionally, I would like to thank Dr. Don Freed, Dr. Anthony Radford, and

Ericka Olsen for being a part of my thesis committee. Each of you brought important and

educational aspects to this thesis. I consider myself lucky to have such intelligent and

well-versed members on this committee. Thank you for helping me further my graduate

education.

Thank you to my friends and cohort for always encouraging me and cheering me

on. These past 2 years would not have been possible without each and every one of you.

TABLE OF CONTENTS

Page

LIST OF TABLES ............................................................................................................ vii

LIST OF FIGURES ......................................................................................................... viii

CHAPTER 1: INTRODUCTION ....................................................................................... 1

CHAPTER 2: LITERATURE REVIEW ............................................................................ 4

VFEs as Holistic Voice Therapy ................................................................................. 4

Singing Exercises ........................................................................................................ 7

Vocal Function Exercises ......................................................................................... 13

Summary ................................................................................................................... 28

CHAPTER 3: METHODS ................................................................................................ 30

Research Design ........................................................................................................ 30

Participants ................................................................................................................ 31

Setting ....................................................................................................................... 32

Procedures ................................................................................................................. 32

CHAPTER 4: RESULTS .................................................................................................. 41

Maximum Phonation Frequency Range .................................................................... 42

Maximum Phonation Time ....................................................................................... 44

Jitter ....................................................................................................................... 46

Shimmer .................................................................................................................... 47

CHAPTER 5: DISCUSSION ............................................................................................ 52

Limitations ................................................................................................................ 57

Recommendations ..................................................................................................... 60

Conclusion ................................................................................................................ 61

REFERENCES ................................................................................................................. 63

Page

vi vi

APPENDICES .................................................................................................................. 67

APPENDIX A: QUESTIONNAIRE ................................................................................ 68

APPENDIX B: HEARING SCREENING FORM ........................................................... 70

APPENDIX C: RECRUITMENT FLIER ........................................................................ 72

APPENDIX D: CONSENT FORM .................................................................................. 74

APPENDIX E: DAILY PRACTICE CHART .................................................................. 76

LIST OF TABLES

Page

Table 1 Busk and Serlin’s (1992) d Statistic (Maximum Phonation Frequency Range) ............................................................................................................... 44

Table 2 Busk and Serlin’s (1992) d Statistic (Maximum Phonation Time) ..................... 46

Table 3 Busk and Serlin’s (1992) d Statistic (Jitter) ........................................................ 49

Table 4 Busk and Serlin’s (1992) d Statistic (Shimmer) .................................................. 51

LIST OF FIGURES

Page

Figure 1. Maximum phonation frequency range across participants ............................... 43

Figure 2. Maximum phonation time across participants .................................................. 45

Figure 3. Jitter across participants .................................................................................... 48

Figure 4. Shimmer across participants ............................................................................. 50

CHAPTER 1: INTRODUCTION

The purpose of the present research study was to determine the efficacy of Dr.

Joseph Stemple’s Vocal Function Exercises (VFEs) in increasing maximum phonation

frequency range and maximum phonation time, and in decreasing jitter and shimmer in

normal adult male-trained singers through the use of a multiple baseline across

participants design. Singing involves a complex manipulation of laryngeal functions to

produce musical sounds. This is achieved through the coordination and balance of several

subsystems, including respiration, phonation, resonation, and articulation. Stemple’s

VFEs are classified as a form of physiologic voice therapy. Physiologic voice therapy

includes programs and techniques that are designed to directly modify or alter the

physiology of the vocal mechanism (Stemple, Roy, & Klaben, 2014). The goal of

physiologic voice therapy techniques is to restore balance among the subsystems of

airflow: laryngeal muscle strength, balance, and coordination. Stemple’s VFEs are

designed to improve the balance between these subsystems of voice production.

For this study, the independent variable was treatment utilizing Stemple’s VFEs

program. The dependent variables were maximum phonation frequency range, maximum

phonation time, jitter, and shimmer. Maximum phonation frequency range is the

measurement determined by subtracting the lowest pitch produced from the highest pitch

produced, excluding the production of glottal fry or falsetto. Maximum phonation time is

determined by measuring the longest duration of a single note held on a single syllable

(Stemple et al., 2014). Maximum phonation frequency range and maximum phonation

time are important aspects of singing that are often targeted for improvement (Stemple,

Lee, D’Amico, & Pickup, 1994).

Jitter is a measurement of cycle-to-cycle variations in the frequency of vocal fold

vibrations, and is therefore a reflection of pitch stability in the voice. Shimmer is a

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measurement of cycle-to-cycle variations in the amplitude of the vocal fold vibrations,

and is also reflected in the stability of a voice. Jitter and shimmer percentages that fall

below a certain threshold will contribute to a desirable vocal quality (Stemple et al.,

2014). For jitter, the threshold is no more than 1.04%, and for shimmer it is no more than

3.810% (KayPENTAX, 2011a). A high percentage of jitter or shimmer that falls above

these thresholds may be perceived as vocal roughness or instability and is therefore

undesirable for any speaker but in particular for a trained singer. Therefore, a low

percentage of jitter and shimmer is most desirable. These measurements differ depending

on the mechanisms of the individuals’ voice, gender, and his or her level of training.

The purpose of this study was to determine if Stemple’s VFEs are a technique that

could be used by healthy adult male trained singers to increase their maximum phonation

frequency range and maximum phonation time and to decrease jitter and shimmer.

Therefore the hypotheses for this study were:

1. Participants who perform VFEs correctly two times, twice a day for 8 weeks,

will significantly increase their maximum phonation frequency range and

maximum phonation time.

2. Participants who perform VFEs correctly two times, twice a day for 8 weeks,

will significantly decrease their jitter and shimmer.

Several research studies have been conducted to evaluate the effectiveness of

singing exercises and VFEs. Singing exercises were noted to improve overall vocal

quality for singers prior to performing, rehearsing, or both (Gish, Kunduk, Sims, &

McWhorter, 2012; Van Lierde et al., 2011). Trained singers stated that singing exercises

enhanced their vocal flexibility and felt their voices were properly aligned for singing

(Elliot, Sundberg, & Gramming, 1992; Gish et al., 2012; Van Lierde et al., 2011).

VFEs were described by Stemple (2005) as a holistic voice therapy approach,

meaning that they are a treatment that could enhance the vocal quality of an individual

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with a normal healthy voice and improve upon an individual with a voice disorder.

Holistic health focuses on the body as a whole and the interdependent parts that help

create a healthy individual. Stemple’s VFEs assist in balancing and strengthening the

laryngeal musculature and balancing the three subsystems or interdependent parts

(respiration, phonation, and resonance) (Stemple et al., 2014). The VFEs are thought to

enhance the overall sound quality of the normal voice and trained singing voice when one

maintains a healthy lifestyle (Stemple, 2005).

Previous research studies have been conducted on VFEs with a variety of

populations (individuals with disordered voices, individuals with normal voices, and

trained singers). Researchers found a significant improvement in acoustic measures

(fundamental frequency, jitter, and frequency range) and aerodynamic measures

(phonation volume, flow rate, and maximum phonation time) for the participants’ overall

speaking voices (Croake, Andreatta, & Stemple, 2017; Elliot et al., 1992; Ellis &

Beltyukova, 2011; Gish et al., 2012; Gorman, Weinrich, Lee, & Stemple, 2008; Guzman,

Angulo, Muñoz, & Mayerhoff, 2013; Sabol, Lee, & Stemple, 1995; Stemple et al., 1994;

Tay, Phyland, & Oates, 2012; Van Lierde et al., 2011). These studies focused on

improving voices in various populations, but the proposed study expanded upon the

reviewed studies regarding the population of normal adult-trained singers.

CHAPTER 2: LITERATURE REVIEW

A comprehensive review of literature concerning the effectiveness of vocal

exercises was completed. The literature involved normal voices, trained singing voices,

and disordered voices as well as vocal warm-up exercises and VFEs. Subject populations

included in the research review consisted of both singers and non-singers and represented

those with typical voices as well as disordered voices. The VFEs are an evidence-based

treatment for individuals with disordered voices and are suspected to improve upon the

skills of those with a normal voice or a professional voice. The review also evaluated

literature on singing and vocal warm-up exercises and the effectiveness of these

exercises.

Stemple’s VFEs “are a series of voice manipulations that were designed to

strengthen and balance the laryngeal musculature and to balance airflow to the muscular

effort” (Stemple et al., 1994, p. 271). VFEs are intended to build upon and improve the

skills currently present in an individual. Trained singers often wish to learn more

technique to enhance their vocal skills. Therefore, these exercises could benefit the

participants by providing them with a tool for improving their singing voices. This study

has the potential to contribute to the limited research on VFEs, especially with trained

singers. This literature review examines the effects of general vocal exercises and VFEs

on singers, non-singers, and disordered voices.

VFEs as Holistic Voice Therapy

Voice therapy goals were built upon the ideas of speaking with adequate

loudness, a clear tone, age and gender appropriate pitch, natural vibrato, and prosody

which accurately relays the meaning of the message perceived (Stemple, 2005). To obtain

a healthy voice, one must possess an overall healthy body and healthy lifestyle.

According to Stemple (2005), “holistic health is based on the concept that a whole is

5 5

made up of interdependent parts” (p. 132). This is referring to the idea that many parts of

the body make up the entire body; therefore, all parts should be considered when looking

at the overall health of an individual. Stemple (2005) stated that voice improvement is not

just for the individual with a voice disorder but also for individuals who want to enrich

their overall vocal performance for an enhanced sound quality. According to Stemple

(2005), holistic health focuses on the idea that there is always a way to improve an

individual’s overall health and well-being, even if an individual is already considered

healthy. This approach to health also utilizes a wellness line where as the degrees of

health status are shown from left to right, with left being death while right is the

maximum degree of health. The center of the degree of wellness indicates no illness, yet

demonstrates that there is room for improvement (Stemple, 2005).

VFEs fit within the model of holistic health simply because they are a treatment

that can help improve the voice quality of individuals with disordered voices, as well as

those who are healthy. Stemple (2005) listed three reasons why VFEs encompass a

holistic approach:

1. Vocal health does not end at what is considered to be a normal voice. Those

with disordered voices or normal voices can improve upon their overall vocal

quality and continue to the right side of the wellness line.

2. Individuals assume responsibility for their own health and improving upon

their current health status.

3. The voice is created by interdependent parts involving respiration, phonation,

and resonance. To achieve a normal and healthy voice, these three interdependent

parts must balance each other out equally and work together (Stemple, 2005).

Stemple based the principle of VFEs on Bertram Briess’s vocal exercises, which

focused on creating a balance within the laryngeal musculature and reducing

hyperfunction (Stemple, 2005). Stemple (2005) used this principle to create VFEs,

6 6

believing these exercises could be used for treatment of both vocal hyperfunction and

vocal hypofunction. According to Stemple (2005), “normal voice production depends on

a relative balance among three subsystems: airflow, supplied by the respiratory system;

laryngeal muscle strength, balance, coordination, and stamina; and coordination among

these and the supraglottic resonators (pharynx, oral cavity, nasal cavity)” (p. 133). When

teaching the exercises, it is important to teach abdominal breathing, or diaphragmatic

breathing, to posture the vowel prior to voicing, and activate voicing with an easy onset

of the vocal folds. All three of these points are addressed through the VFEs, and therefore

they are considered a holistic voice treatment approach.

Many people do not think of the laryngeal mechanism as being similar to other

muscles or structures in the body. However, Stemple (2005) compared rehabilitation of

the laryngeal mechanism to rehabilitation of the knee. He described the process of

rehabilitation of the knee as first a period of rest to help lessen anymore harm from the

acute injury. Following the resting period, the knee is walked on and exercises are

recommended to begin to strengthen and stabilize the musculature. This rehabilitative

process for the knee is similar to what might be done for the voice. After an acute vocal

fold injury, vocal rest may be required, followed by allowing the person to speak, and

then introducing treatment exercises designed to return the voice to as normal of a state

as possible.

In summary, VFEs are considered to encompass principles of holistic therapy

because they focus on improving not only the disordered voice, but also the normal voice.

VFEs achieve this by focusing on the three subsystems of respiration, phonation, and

resonance. Additionally, VFEs help balance the three subsystems to establish a

physiological system for the normal voice to be integrated into other forms of effective

communication. Therefore, VFEs are also classified as a form of physiologic voice

therapy.

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Singing Exercises

Singing exercises have been studied by many researchers as a treatment technique

for individuals with disordered voices, individuals with normal voices, and trained

singers. Singing exercises are also known to be used as vocal warm-ups for singers prior

to performances and rehearsals. The following studies evaluated singing exercises or

warm ups as they pertained to the anatomy and physiology of the vocal mechanism,

prevention of vocal fold injury, and overall vocal quality after performance of the

exercises.

Gish et al. (2012) surveyed 117 participants who were trained singers regarding

vocal warm-up practices and their opinions concerning vocal warm-ups. Warm-ups are

vital to singers and other professional voice users, just as stretching and warming up are

to an athlete. It is believed that vocal warm-up exercises contribute to the prevention of

vocal fold injury in professional voice users. The purpose of this study was to explore

how often and how long singers utilize warm-ups, evaluate the differences between

warm-up sessions in singers of varying skill levels, establish which warm-up exercises

are used the most, gain perspective on singers’ opinions of warm-ups and prevention of

injury, and finally to gather data regarding the amount of injury experienced by singers.

Gish et al. (2012) targeted undergraduate and graduate singers as well as trained

professionals. The survey contained 69 questions which included open-ended responses

as well as yes/no questions. The survey questionnaire focused on topics such as, how

often they used warm-ups, whether these sessions were consistent, how long they

warmed-up, and what exercises they used for their warm-ups. The researchers listed

many types of warm-up exercises found in the literature, and the participants were

required to select which one(s) they used from the multiple-choice list. In the

questionnaire, the researcher required information regarding the participants’ age, gender,

current academic level, and number of years they had taken voice lessons. Additionally,

8 8

the researchers asked questions about the type of vocal warm-ups, the participants’ views

on warm-ups, how much they sang each day and for how long, whether they participated

in any vocal abuse, whether they had any history of vocal issues, and whether they had

any medical disorders that could be associated with a voice disorder.

Gish et al. (2012) found that 54% of the participants reported consistently

warming up prior to performing. It was noted that more participants reported warming up

prior to a solo performance rather than before an ensemble performance. The most

reported types of non-vocal warm-ups were muscle stretching exercises (e.g., neck),

breathing exercises, and postural exercises. The most common singing warm-ups were

ascending and descending five-note scales, ascending and descending arpeggios, and

glissandos (gliding up and down). The participants reported that warm-ups were

important and helped increase the flexibility of their voices. Interestingly, few

participants agreed that warm-ups prior to singing helped prevent vocal fold injury.

Overall, Gish et al. (2012) found that the older the singer was, the more likely he

or she would perform vocal warm-ups prior to singing. They also found that the duration

of vocal warm-ups varied greatly among singers and that the typical duration for warm-

ups was about 5 to 10 minutes. Only a few participants agreed that if they did not

complete warm-ups they could injure their voices; however, they still completed them

due to an enhanced singing quality afterwards. Gish et al. (2012) noted that limited

research has been conducted on vocal warm-ups as they pertained to vocal fold injury.

These authors felt that further research was needed on the topic in order to support the

importance of vocal warm-ups.

When singers do not take precautions to care for their voices or perform vocal

warm-ups prior to singing, a higher risk of development of vocal pathologies could occur.

Spencer (2009) reviewed the importance of vocal exercises as a part of vocal therapy.

9 9

Furthermore, he explained that singers could demonstrate the following vocal behaviors

that could lead to vocal pathologies:

1. Excessive vibration in the higher register.

2. Consistent discrepancy of the singer’s Fach, or voice part.

3. Persistent vocal intensity or voce piena, and lack of awareness when fatigued

and requiring rest.

4. Disregard for early signs of vocal injury, such as:

a. Compensatory strain due to lack of easy phonation;

b. Disturbed tonal onset;

c. Lessened breath control;

d. Decreased intensity, or lack to differ intensity;

e. Change in voice part, or loss of pitch range;

f. Break in the passagio, or transition between registers;

g. Diplophonia, voice breaks, burring; and

h. Longer period of vocal recovery following a performance.

5. No warm-up prior to performance.

6. Inadequate amplitude.

7. Poor vocal hygiene and behaviors (Spencer, 2009).

These characteristics of vocal pathologies have been observed throughout

considerable amounts of research. Spencer (2009) stated that singers were at higher risk

for vocal pathologies if there was a lack of warm-up prior to singing. Considering few

singers in the study conducted by Gish et al. (2012) believed in the importance of warm-

ups, further education is required for singers regarding vocal exercises in enhancing vocal

quality and preventing injury.

Additionally, it is imperative that the vocal mechanism is aligned properly for

precise execution of the singing exercises to create the foundation for proper singing

10 10

technique. For singing, the ideal position is described as upright and low. It is suggested

that this particular position helps eliminate poor vocal technique, such as forced

adduction of the vocal folds while singing. Many vocal exercises aim to achieve this

position for training (Elliot et al., 1992). Elliot et al. (1992) examined whether this

positioning of the larynx was successful in facilitating proper technique while performing

a specific vocal exercise created for disordered voices. The study included seven

participants. Two participants had hyperfunctional dysphonia phonasthenia, a functional

audible voice disorder; three participants were trained singers; and two participants were

untrained individuals with healthy voices. The researchers used a tracking multichannel

electroglottograph system (TMEGG), presented by Rothenberg (1992), which contained

electrodes that were placed on the participants’ necks in order to obtain positioning of the

larynx at rest and during exercises. Prior to taking data, the TMEGG was calibrated,

while the larynx was at rest and during a sustained single note on nonsense syllables that

contained a prolonged /b/ sound with a vowel. These syllables began as consonant vowel

(CV) and gradually increased in variation.

Elliot et al. (1992) discovered that when subglottic air built up below the vocal

folds, the larynx was at a higher upright position. However, if a balance was established

between the subglottic pressure and the intraoral pressure, the larynx relaxed into a lower

position that was required for proper singing technique. They found that this positioning

came from a change in air pressure throughout the different cavities. It has been observed

that hyperfunctional voices typically produce sound with an elevated larynx; therefore,

this research could be beneficial for understanding the disordered voice. However, the

research could also provide further information to professional voice users, such as

singers, in educating them regarding the anatomy and physiology of the larynx and what

changes might occur while singing. The researchers concluded that lowering the position

11 11

of the larynx could reduce hard glottal attacks and facilitate phonation with an easy onset

of the vocal folds.

Van Lierde et al. (2011) conducted a randomized pretest-posttest control group

design that evaluated the effectiveness of a 30-minute vocal warm-up program on vocal

quality measures in female students studying speech-language pathology. The study

included 45 participants in both the experimental and control groups. Effects of vocal

warm-up exercises were evaluated for aerodynamic measures, vocal range, acoustic

changes, and the Dysphonia Severity Index (DSI). The DSI is intended to establish an

objective and quantitative comparison of vocal quality measurements (MPT, highest

frequency (F-high), lowest intensity (I-low), and jitter).

Van Lierde et al. (2011) collected pre- and posttest data before and after the

experimental group performed the 30-minute warm-up program (WU) while the control

group was on vocal rest for the 30-minutes. The WU program consisted of stretching

exercises to initiate movement in the cervical muscles and vocal exercises. The first

stretching exercise innervated the sternocleidomastoid by tilting the head back. The

second exercise activated the trapezius muscle. The final exercise stimulated the

mylohyoid muscle which innervates the base of the oral cavity for tongue height. The

vocal exercises consisted of the following tasks:

1. Gentle glide with an open mouth approach on the vowels, /a/, /e/, /u/, /ie/, /ij/.

The purpose of this exercise was to provide the participants with a gentle, easy

onset of the vocal folds with the least amount of strain.

2. Glottal fry on the same vowels as the previous exercise, except instead of /ij/,

the performer used the vowel /ɛi/. This exercise was intended to provide a

shortening of the vocal folds and challenges the performer to sustain the airflow.

3. As opposed to the previous exercise, the hyper high-blowing exercise intended

to lengthen the vocal folds in order to create a higher pitch. This exercise required

12 12

the performer to blow air through tightly closed lips and is similar to a semi-

occluded exercise with same principle of taking any constriction of the laryngeal

musculature.

4. Similar to the previous exercise, voiced tongue trills reduced vocal fold impact

due to removing the strain off the larynx.

5. Resonance exercises focused on lengthening the vocal tract and creating

resonance in the resonating cavities as opposed to the larynx.

6. Ascending and descending tones aimed to contract the vocal folds and the

cricothyroid muscle to create ascending and descending tones.

7. Hand-over-mouth technique was similar to a semi-occluded posture exercise.

The goal of this exercise was for the participant to focus the tone around the lips

while their hand covers the oral cavity, therefore reducing compression of the

larynx.

Van Lierde et al. (2011) found that a vocal WU program demonstrated a desired

treatment effect by increasing the DSI measurement (I-low and F-high) and fundamental

frequency (p value significance = <0.05). The control group did not demonstrate any

improvement from the pretest to the posttest. Overall, these results were shown to support

the hypothesis of increased vocal quality measures after 30-minutes of a vocal WU

program.

Van Lierde et al. (2011) noted several limitations that warranted consideration for

future research on vocal warm-ups. The researchers did not require qualitative, self-rating

data prior to the baseline measurements. Maintenance following the posttest was not

attempted, and, therefore, it is unknown if the desired treatment effect was maintained

after treatment was discontinued. Additionally, there was a lack of understanding

regarding the specific reasons why the WU program improved vocal quality. Despite the

various limitations, the research conducted by Van Lierde et al. (2011) concluded that a

13 13

vocal WU program is key to improved vocal quality. It is assumed that this study could

benefit professional voice users, especially considering how important vocal quality and

precision of singing is to professional voice users. The authors noted that these WUs

could be especially useful to speech-language pathologists who want to help their voice

clients achieve improved vocal quality and overall vocal health.

In summary, the research studies illustrated above, found that vocal warm-ups

provided an improved vocal quality and flexibility needed for adequate singing (Gish et

al., 2012; Van Lierde et al., 2011). Elliot et al. (1992) further explained that the ideal

positioning of the larynx for singing is a low, upright posture to reduce unwanted vocal

hard glottal attacks and enhance easy onset phonation. Overall, singing exercises were

recommended prior to performing, rehearsing, and speaking for enhanced vocal quality

and proper alignment of the laryngeal mechanism (Elliot et al., 1992; Gish et al., 2012;

Van Lierde et al., 2011).

Vocal Function Exercises

A number of researchers have investigated the relationship between VFEs and

various vocal measurements (maximum phonation time, flow rate, phonation volume,

open quotient, average airflow, peak airflow, and minimum airflow). The following

studies were reviewed in regards to non-singers with normal voices, trained singers, and

individuals with voice disorders.

Non-singers with Normal Voices

Many researchers have examined the effects of VFEs as a whole; however,

Croake et al. (2017) used a single group design to compare the VFE semi-occluded

mouth posture on the word /nol/ with a lip buzz to a sustained /o/ on glottal airflow

measures in normal voices. Glottal airflow measures consisted of (a) average airflow, (b)

14 14

peak airflow, (c) minimum flow, (d) maximum flow declination rate (MFDR), (e) open

quotient (OQ) and, (f) skewing quotient (SQ).

Croake et al. (2017) included eight male participants with normal healthy voices

between the ages of 22-40 years. Prior to data collection, the participants were trained to

properly perform the VFE semi-occluded mouth posture with lip buzz. The researchers

described the semi-occluded mouth posture as similar to a whistle. Croake et al. (2017)

stated that this required tightly round lips while the pharynx created an “inverted

megaphone shape” (p. 244) while maintaining a forward sound (lip buzz). Audible and

vibratory feedback of the lip buzz to the researchers and the participants, respectively,

confirmed proper execution of the exercise. The participants switched between the /nol/

with lip buzz and the sustained /o/ vowel to ensure proficiency of the exercises. Data

were computed on flow glottograms via the inverse-filtered oral airflow signal through a

pneumotachograph mask.

Croake et al. (2017) analyzed data using the Shapiro-Wilk W test and paired t

tests. The p value indicated a significant (<0.05) improvement with minimum flow and

OQ with the VFE semi-occluded mouth posture as compared to the sustained /o/ vowel.

It was unclear to the researchers how minimum flow might have increased. Croake et al.

(2017) stated that visualization of the vocal folds during the /ol/ vowel would be

necessary to declare the cause of the increased minimum flow. The increase of OQ in this

study could have been due to increased vocal fold amplitudes which was thought to occur

because the semi-occluded position kept the vocal folds separated for a longer period of

time by suspending forward airflow, therefore increasing amplitudes (Croake et al.,

2017).

Overall, Croake et al. (2017) found that there was overall improvement when the

participants performed the lip buzz exercise as opposed to the sustained /o/ vowel across

all measurements. Further research of the VFE semi-occluded mouth posture exercise

15 15

with other vowels would be valuable to future studies. However, it is understood that the

/o/ vowel was used because it is the closest to the semi-occluded /nol/ exercise. This

research showed that the semi-occluded mouth posture could take the stress off the vocal

folds, redirecting it to the lip buzz, and thereby creating increased vocal fold amplitudes.

Stemple et al. (1994) used a pretest-posttest control group design to evaluate the

effect of VFEs on various vocal measures in the normal voice. The vocal measures

consisted of acoustic voice features (fundamental frequency, jitter and frequency range)

and aerodynamic voice features (phonation volume, flow rate, and maximum phonation

time). The participants included 35 female graduate students with normal voices that met

the criteria for the study. Each participant was randomly assigned to one of the three

groups: the experimental group, the control group, or the placebo group.

Stemple et al. (1994) had graduate clinicians who were taught by a certified

speech-language pathologist provide instruction on VFEs to the participants in the

experimental group. VFEs consisted of four steps that were repeated two times each: (a)

maintain /i/ for as long as possible on a consistent, comfortable note, (b) glide from the

lowest to the highest note on /o/, (c) glide from the highest note to the lowest note on /o/,

and (d) maintain the musical notes of middle C and D, E and F, and G five notes above

middle C for as long as possible on /o/ (Stemple et al., 1994).

Stemple et al. (1994) provided the same information regarding the study to the

experimental and placebo groups. However, the exercises assigned to the placebo group

consisted of reading a passage and chanting sentences at a comfortable level. These

exercises were chosen by the researchers because they were believed to have no direct

effect on improvement of the voice. The control group did not receive treatment. Both the

experimental and placebo groups were required to perform the treatment twice a day, two

times each. The participants recorded these sessions and met weekly with a clinician for

review. Data were collected prior to beginning treatment and 28 days later following

16 16

treatment. After collection of data, a statistical analysis was conducted utilizing

multivariate analysis of variance (MANOVA) and ANOVAs (p value significance =

<0.05) (Stemple et al., 1994).

Stemple et al. (1994) found that the statistical analysis results indicated a

significant improvement of phonation volume, maximum phonation time, and decrease of

flow rate measurements in the experimental group from the pretest to the posttest. The

results also showed no change in the control group or the placebo group. However,

participants in the placebo group reported improvement in their overall vocal quality and

appreciated the exercises.

Stemple et al. (1994) described the possible reasons for an increase of phonation

volume and maximum phonation time and decrease in flow rates. In regards to phonation

volume, VFEs are suspected to help improve the strength of the respiratory muscles.

Therefore, the participants may have learned to inspire and expire larger and smaller

amounts of their overall respiratory volumes, resulting in an increased lung capacity for

phonation. It is suspected that flow rate decreased significantly due to enhanced balance

and strength of the laryngeal musculature. The increase of phonation volume and

decrease of flow rate ultimately led to an increase in maximum phonation time. The

authors concluded that VFEs improved the participants’ vocal function, and they

recommended that future research focus on the use of VFEs in individuals with voice

disorders.

Ellis and Beltyukova (2011) used a pretest-posttest control group design to

examine the effect of compliance monitoring of VFEs on maximum phonation time,

maximum phonation frequency range, and phonation quotient with normal voices. The

participants included 20 voluntary female speech-language pathology graduate students

with normal voices. Each participant was randomly assigned to either the monitored

compliance group or the unmonitored compliance group, each involving 10 participants.

17 17

The researchers provided instructions to both groups on how to properly perform VFEs,

as well as a CD (Stemple, 2006a) recorded by Dr. Stemple to use for practice. The

monitored and unmonitored groups performed VFEs twice a day, two times each for 4

weeks. Those in the monitored group were required to submit daily recordings of their

performance of VFEs, while the unmonitored group did not.

Ellis and Beltyukova (2011) gathered data before and after VFEs. Data gathered

for phonation times required the participants to hold out one note on /a/ for as long as

possible. For maximum phonation frequency ranges, the participants were required to

hold /a/ on scaled notes until they reached their lowest and highest pitch, measured by the

Visipitch IV Real Time Pitch program (KayPENTAX, 2011b). The best of the three trials

for maximum phonation time and maximum phonation frequency ranges were used. The

phonation quotients were analyzed by the ratio of the participants’ vital capacity, via

Micro Plus Spirometer, and maximum phonation time.

Ellis and Beltyukova (2011) analyzed data by using a between- and within-

subjects analysis of variance (ANOVA). The researcher compared results of the

monitored treatment to the results of the unmonitored treatment. Results of the posttest

indicated that the monitored group significantly improved in maximum phonation times

and maximum phonation frequency ranges as compared to the unmonitored group. These

findings were possibly the effect of the participants knowing that they were being

monitored, and, therefore they consistently and accurately performed VFEs. Monitoring

of the participants could contribute more control within the study; however, monitoring

of VFEs as treatment may not be realistic in a clinical setting, and therefore further

research is needed without monitoring.

In summary, the reviewed studies found that VFEs had a positive impact on non-

singers with normal voices. The use of VFEs improved maximum phonation time (Ellis

& Beltyukova, 2011; Stemple et al., 1994); maximum phonation frequency range (Ellis &

18 18

Belyukova, 2011); phonation volume and flow rate (Stemple et al., 1994); and minimum

flow and open quotient (Croake et al., 2017). Croake et al. (2017) also found that the

VFE semi-occluded mouth posture exercise enhanced glottal airflow measures as

opposed to an /o/ vowel. Stemple et al. (1994) and Ellis and Beltyukova (2011) both

concluded that, when performed properly and controlled, VFEs can enhance the normal

speaking voice.

Trained Adult Singers

The following studies evaluated VFEs and their effect on various vocal measures

in trained adult singers. Accurate technique is the important foundation for proper singing

and building this foundation requires proper airflow, adequate laryngeal muscle

movement, and appropriate supraglottic tone placement (Sabol et al., 1995). As a

physiologic voice therapy technique, VFEs have the potential to positively impact these

vocal subsystems.

Sabol et al. (1995) used a pretest-posttest control group design to evaluate the

effects of VFEs on vocal measures when they were integrated into singers’ everyday

practice. The researchers evaluated acoustic measures (fundamental frequency, jitter, and

frequency range), aerodynamic measures (phonation volume, flow rate, and maximum

phonation time), and videostroboscopic measures. The participants included 20 graduate-

level voice majors between the ages of 21-39 who were taking weekly voice lessons from

a professor in the music department. The participants were strategically divided into an

experimental group and a control group. The researchers decided to divide the groups

based upon the participants’ experience, level of singing, age, and sex (three males and

seven females in each group). The experimental group was taught how to properly

perform VFEs, and the exercises were added into their practice sessions, twice a day, two

times each. The control group continued their current practice sessions as previously

19 19

completed. Both groups were required to continue their voice lessons and training and

they were instructed to avoid engaging in vocally abusive behaviors (e.g., yelling) (Sabol

et al., 1995).

Sabol et al. (1995) gathered data for acoustic measures and aerodynamic measures

with a Visi-Ptich (Kay Electrometrics model 6097) and a Nagashima Phonatory Function

Analyzer (model PS 77H). Additionally, data were collected through questionnaires and

case histories that revealed the participants’ extracurricular activities, voice type, medical

history, and schedule of singing. Similar to Stemple et al. (1994), the researchers

conducted the study for 4 weeks, collecting data 28 days apart for pretest and posttest

data collection.

Sabol et al. (1995) completed a statistical analysis of the data by utilizing a

multivariate analysis of variance (MANOVA) and an ANOVA to assess for significance

through a p value. The study found that the experimental group demonstrated significant

differences between pre- and posttest data in regards to phonation volumes, decreased

airflow rates, and increased maximum phonation times. This study revealed higher

phonation volumes to that of Stemple et al. (1994) with non-trained singers and required

further investigation as to an explanation. In regards to the decreased airflow rates, it was

suspected that VFEs assisted in enhancement of vocal fold adduction, adequate

phonation, and subglottic pressure. For maximum phonation time, it was thought to have

increased due to an easy onset of phonation with proper glottal closure at low lung

volumes resulting in an increase of phonation time (Sabol et al., 1995).

Sabol et al. (1995) demonstrated that VFEs had a beneficial effect on trained

singers without a voice disorder. These authors concluded that further research is needed

to evaluate VFEs on younger singers who are in their undergraduate program and who

are not as advanced as graduate trained singers are. This study showed, however, that

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even advanced trained singers benefited from use of VFEs and that they could use them

as a long term, practice regimen.

A similar study was conducted by Tay et al. (2012) who used a prospective

experimental design to examine the effects of VFEs on measures of vocal function.

Participants included 22 aging choral singers. The vocal measures evaluated were

auditory-perceptual voice features (breathiness, roughness, and strain), acoustic voice

features (phonation frequency range, jitter, shimmer, and noise to harmonic ratio [NHR]),

and maximum phonation time. Each participant was randomly selected to either the

experimental VFEs group or the control group, consisting of eleven participants each.

The participants in the experimental group were required to attend four sessions with the

researcher to ensure proper performance of VFEs throughout the study. The control

group was required to meet with the researcher two times throughout the 7 weeks of the

study. Both the experimental and control groups were required to document their singing

hours and practice times.

Tay et al. (2012) completed a statistical analysis of the data by utilizing the Mann-

Whitney U test and a paired t test. The results of the t test did not indicate any statistical

significance between the experimental group and control group. However, the results of

the Mann-Whitney U test showed the control group documented more singing hours than

the experimental group during the study. With regards to the auditory-perceptual voice

features, only roughness showed a statistical significant decrease for the experimental

group. It is suspected that this was due to the improvement of the vibration of the vocal

folds since performing VFEs. The auditory-perceptual voice features revealed that the

experimental group increased their phonation frequency range, and both groups

decreased jitter, shimmer, and NHR. This was possibly because the control group

documented more singing hours than the experimental group. Additionally, it was

believed that these exercises improved the adduction of the vocal folds and increased

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vibrations which lead to increased phonation frequency range, and therefore, a decreased

jitter and shimmer.

Tay et al. (2012) gave a self-assessment that consisted of a scale from 0 to 6, 0

represented strongly disagree and 6 represented strongly agree. The participants were

requested to evaluate whether there was a change in their voice after the training, whether

they would continue VFEs on their own, and whether their voice improved due to

implementation of VFEs. Results of the self-assessment showed that the participants in

the experimental group reported that their voices fatigued less and that they could sing

longer after performing VFEs. Overall the study showed that the use of VFEs improved

the overall voice quality in the experimental group.

Guzman et al. (2013) evaluated the effectiveness of VFEs in regards to the long-

term average spectrum of pop singers with normal voices. The researchers compared

VFEs to traditional vocal warm-up exercises that singers use in their everyday practice

regimen. Various acoustic vocal measures included alpha ratio, L1 – L0 ratio, and singing

power ratio (SPR). The researchers recruited 38 pop singers with normal voices and

divided them into two groups: an experimental group consisting of 20 participants and a

control group, consisting of 18 participants. Both groups were required to attend a

training session prior to treatment to receive instruction on the exercises they would be

performing. The experimental group was taught VFEs, and the control group was

instructed on traditional vocal warm-up exercises.

Guzman et al. (2013) recorded the participants before and after the exercises were

completed. They were required to read a given text aloud as well as sing “Happy

Birthday” in a comfortable key. The experimental group performed all four VFEs, and

the participants were allowed to adjust the musical notes to their voices, per the protocol

(Stemple, 2000). The control group learned the traditional vocal warm-up exercises,

which consisted of singing a simple tune on the vowel /a/ while singing in intervals of

22 22

thirds. Participants adjusted the musical notes to their voices, similar to the protocol for

VFEs.

Guzman et al. (2013) statistically analyzed the data by utilizing the long-term

average spectrum (LTAS) analysis. A statistically significant difference was found

between the experimental group and control group in regards to speaking voice and

singing voice. The alpha ratio and SPR increased significantly in the VFEs experimental

group. These results showed that VFEs had an instant effect on the spectrum of the

normal voice of singers. Such an immediate effect would support the use of VFEs for

vocal warm-ups. It is unclear, however, as to whether the same effect would occur in a

non-singer or if the instant effectiveness was due to the prior training of the singer. The

researchers suggested that future research should explore the use of VFEs as warm-up

exercises.

In summary, Sabol et al. (1995), Tay et al. (2012), and Guzman et al. (2013)

conducted similar studies involving trained singers with different demographic

characteristics. These studies contributed reliable data and suggested that VFEs enhanced

the overall normal trained singing voice. Guzman et al. (2013) also suggested that VFEs

could lend themselves as a simple, and immediate solution for vocal warm-ups in singers.

Disordered Voices

VFEs were originally created for individuals with voice disorders to assist them in

balancing the laryngeal musculature and improving their overall vocal health and quality.

The exercises claim to help stabilize and balance the laryngeal musculature for proper

vocal production (Sabol et al., 1995; Stemple et al., 1994). A number of studies have

investigated VFEs and their potential benefits for individuals with disordered voices.

It is understood that about 5-10% of the working population in the United States

are professional voice users, including singers (Roy et al., 2001). However, teachers are

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the largest population of professional voice users, meaning that they use their voice

throughout the day to fulfill the duties of their daily work. A study conducted by Roy, et

al. (2001) investigated the effectiveness of two vocal treatments. Participants included 58

teachers with voice disorders. The participants were divided into three groups, two

experimental groups and one control group. The first experimental group consisted of 20

participants who completed a vocal hygiene program (VH) that focused on vocal

education as well as restrictions regarding the amount and type of voice use. The VH

program was based on the assumption that these steps may help improve overall vocal

quality and tissue in the laryngeal musculature. The second experimental group consisted

of 19 participants who performed VFEs. The intention behind VFEs is to restore balance

and strength to the laryngeal musculature (Stemple et al., 1994). Lastly, the control group

consisted of 19 participants who did not receive treatment.

Roy et al. (2001) recruited 11 speech-language pathologists (SLPs) who assisted

in the study and led the treatment sessions for the participants. The SLPs attended a

training session in order to have consistent instruction across sessions with the

participants. The training session included proper demonstration and teaching of VFEs as

well as information on the VH program. The teachers underwent a 6-week treatment

program and met with the SLPs 4 times during that period. The teachers filled out a

Voice Handicap Index (VHI) for pretest and posttest qualitative data. Additionally, a

posttest teacher-questionnaire was administered to gather information regarding prior

voice problems and the benefits of treatment. It was also designed to “assess their

perceived degree of voice improvement and compliance with the treatment program”

(Roy et al., 2001, p. 290).

Roy et al. (2001) concluded that those who completed VFEs demonstrated greater

improvement in the VHI scores as opposed to those in the VH program. The participants

in the VH and control group did not report significant change in their VHI scores. These

24 24

findings were consistent with the teacher questionnaire given after treatment was

completed. Those who performed VFEs reported “more overall voice improvement, as

well as greater ease and clarity of their speaking and singing voice, after treatment” (Roy

et al., 2001, p. 291).

Roy et al. (2001) identified the following limitations in their study. First, the VH

program was utilized as a didactic treatment in that it was not paired with an active

exercise while simultaneously receiving education. VFEs, on the other hand, provided

education as well as exercises to ensure improved musculature. Second, the nature of the

participants’ vocal pathologies or disorders were not clearly defined prior to treatment.

Knowing this information could have helped with the education aspect of the treatments.

Third, it is suspected that some participants may have struggled with complying to the

VH program due to the expectations of changing daily lifestyle activities as opposed to

VFEs that did not necessarily change the participants’ entire lifestyle. Finally, the

researchers noted that using the VHI produced pervasive results, and further research

should be conducted in which quantitative measures are used to assess the differences in

these types of programs. Overall, the researchers concluded that VFEs could be a reliable

method of treatment for individuals with voice disorders.

Vocal fold atrophy, also known as presbylaryngeus, is caused by natural aging

and a change in the tissue or other structures of the vocal folds. This creates a small gap

between the vocal folds resulting in inconsistent hoarseness, decreased loudness,

breathiness, and vocal fatigue (Stemple et al., 2014). Kaneko et al. (2015) conducted a

study utilizing a retrospective pretest-posttest control group design to evaluate the

effectiveness of VFEs on improving vocal measures. Vocal measures consisted of

maximum phonation time, intensity, jitter, and shimmer. Additionally, a

videostroboscopy was conducted to assess for atrophy, bowing, normalized mucosal

wave amplitude (NMWA), and normalized glottal gap (NGG). The study consisted of 22

25 25

participants with vocal fold atrophy who were between the ages of 65 and 81. The

experimental group included 16 participants, and the control group included 6

participants. The participants in the experimental group were required to perform the

VFEs every day, twice a day for 8 weeks.

Kaneko et al. (2015) found that the results revealed limited improvement in the

bowing of the vocal folds with VFEs; however, it was concluded that VFEs did improve

the participants’ overall vibration of the vocal folds. Additionally, a 10 question Voice

Handicap Index (VHI-10) was administered. Results indicated significance between pre-

and post-treatment by utilizing a p value (significance = < 0.05). Furthermore,

researchers found significant improvement in GRBAS, MPT, jitter, NMWA, NGG, and

VHI-10 for VFEs treatment group. It was thought that the stretching and contracting

exercises of VFEs contributed to the improvement of the NMWA, NGG, and jitter.

Furthermore, the researchers stated that VFEs target increased respiration and stamina,

which was suggested to have led to increased MPT (Kaneko et al., 2015). No

improvement was seen within the control group for any measurements analyzed.

Sauder, Roy, Tanner, Houtz, and Smith (2010) evaluated the effects of VFEs on

auditory-perceptual measures, acoustic measures (harmonics-to-noise ratio, jitter,

shimmer, maximum phonation time, and fundamental frequency), visual-perceptual

observations, and self-ratings in individuals with presbylaryngeus. The study consisted of

9 participants (2 women and 7 men) over the age 65 years who were diagnosed with

presbylaryngeus. They were diagnosed with presbylaryngeus if dysphonia was present

and no mucosal disease or bowing was visualized. The researchers decided to initiate

VFEs in this study because VFEs target many vocal variables, such as tension, breath

support, easy onset, and resonance (Sauder et al., 2010). The participants were required to

perform VFEs two times a day, twice each for 6 weeks.

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Sauder et al. (2010) took various measurements utilizing an array of

instrumentation for pre-treatment and post-treatment data. The Multidimensional Voice

Profile (MVDP) (KayPENTAX, 2011a) measured acoustic analysis while participants

recited the “Rainbow Passage.” In regards to acoustic analysis, the participants were

required to recite the “Rainbow Passage” and sustain an /a/ vowel. Auditory-perceptual

ratings were measured by graduate students who listened and rated the “Rainbow

Passage” and provided an overall severity rating. Self-ratings were conducted through the

VHI before and after treatment. Visual-perceptual ratings were obtained via a rigid

videolaryngostroboscopy in order to visualize any changes in the laryngeal musculature.

Sauder et al. (2010) completed a statistical analysis of Wilcoxon signed ranks test

and paired t tests. The results of the statistical analysis revealed no significant changes in

the acoustic aspects of the treatment. In regards to auditory-perceptual ratings, a

significant difference was found between pre- and post-treatment measurements for

breathiness and strain, as well as an overall improvement in the vocal quality. The self-

ratings revealed significant reductions in the overall VHI scores, especially in the area of

dysfunction and phonatory efforts. This indicated that the participants felt that their

overall physical effort to produce sound significantly decreased as a result of VFEs.

Visual-perceptual ratings demonstrated no visual change in the laryngeal musculature.

The researchers proposed that the possible change in breathiness, strain, and reduced

physical effort could be due to modification of respiration and resonance in attempts to

improve glottal closure and effective phonation.

Gorman et al. (2008) conducted a study evaluating the effect of VFEs on

aerodynamic measures (maximum flow rate, minimum flow, peak flow, alternating

glottal airflow, and subglottal pressure) in mature men. The researchers used a pre- and

post-treatment experimental design involving 19 participants ages 60 to 78. All the

27 27

participants displayed presbylarynx by visualization of bowing and glottal gap within the

vocal folds by videostroboscopy.

Gorman et al. (2008) trained the participants in VFEs and determined that the goal

of treatment was to “ensure accuracy of vowel and pitch production on all exercises”

(Gorman et al., 2008, p. 1901). The participants were required to perform the exercises

two times a day, twice each. The treatment was 12 weeks long and the participants met

with the researcher once a week to take measures of maximum phonation time (MPT).

MPT was measured by visualization of a stopwatch. Data regarding aerodynamic

measures were gathered through a pneumotachograph mask which sent signals to a Vetter

Digital Multichannel Recording Adaptor (Model 4000A).

Gorman et al. (2008) completed a statistical analysis of the data utilizing t-tests

and an analysis of variance. Results indicated that MPT significantly improved over the

course of the 12-week treatment and were suspected to be improve without laryngeal

tension or excess intensity (Gorman et al., 2008). In regards to aerodynamic measures, a

significant decrease in glottal airflow and increased subglottic pressure was noted. These

findings were surprising considering the previous lack of glottal closure of the vocal

folds. This study, as well as Kaneko et al. (2015), suggested that VFEs could be an

effective treatment technique for mature participants, especially those with

presbylaryngeus.

In summary, the review of studies that examined VFEs in individuals with

disordered voices found that VFEs had a positive impact on non-singers with a

disordered voice. VFEs were noted to be an appropriate treatment for various ages and

genders with different voice disorders (Gorman et al., 2008; Kaneko et al., 2015; Roy et

al., 2001). Maximum phonation time was observed to significantly improve in males with

disordered voices (Gorman et al., 2008), which relates to the present study evaluating

males who are trained singers. VFEs were also suggested to be the most appropriate

28 28

choice of treatment given that they are a direct, physiological voice treatment as opposed

to a lifestyle change (Roy et al., 2001).

Summary

The reviewed research studies evaluated various vocal warm-up exercises and

various voice treatment techniques, including VFEs, in singers and non-singers with

disordered and healthy voices. Additionally, the studies included a variety of voice

measurements such as auditory-perceptual features, acoustic features, and aerodynamic

features. The present research study evaluated maximum phonation frequency range,

maximum phonation time, jitter, and shimmer as they pertain to trained singers. All of

these measurements were utilized in at least one reviewed study in either individuals with

normal voices, trained singers, or individuals with disordered voices. Several studies

demonstrated that maximum phonation frequency range, maximum phonation time, jitter,

and shimmer could improve with proper execution of VFEs as treatment in a variety of

populations. (Croake et al., 2017; Ellis & Beltyukova, 2011; Gorman et al., 2008;

Guzman et al., 2013; Sabol et al., 1995; Stemple et al., 1994; Tay et al., 2012).

Additionally, the reviewed research showed that VFEs were noted to be an appropriate

and effective treatment for various ages and genders with individuals with voice

disorders, individuals with normal voices, and trained singers (Croake et al., 2017; Ellis

& Beltyukova, 2011; Gorman et al., 2008; Guzman et al., 2013; Kaneko et al., 2015; Roy

et al., 2001; Sabol et al., 1995; Stemple et al., 1994; Tay et al., 2012).

The current research study examined the effectiveness of VFEs in the normal

trained singer’s voice. Additionally, the current research study provides further, detailed

information regarding the effectiveness of VFEs in regards to the population of male,

college-aged trained singers. Results of this study could potentially give singers

additional techniques for those who want to increase their maximum phonation frequency

29 29

range and MPT or decrease jitter and shimmer, thus improving their overall vocal

function.

CHAPTER 3: METHODS

Research Design

The current research study investigated whether VFEs can be used to further

enhance non-disordered voices in trained singers. This study utilized a single-subject,

multiple baseline across participants research design. This particular design allowed for

controlled distribution of VFEs as treatment. No prior research has been conducted on

VFEs while utilizing a single-subject, multiple baseline across participants research

design.

Experimental studies with single subjects have been one of the primary research

designs used within the field of speech-language pathology over the past 20 years

(Hegde, 2003) and are well-suited to exploring the effectiveness of treatment in this field

(McReynolds & Kearns, 1983). Single-subject research designs are widely accepted in a

number of professions, including education, psychology, counseling, and speech-

language pathology (Bordens & Abbott, 2008; Hegde, 2003; Mertens, 2005). Single-

subject designs are the preferred method of evaluating behavioral intervention techniques

(Barlow, Hayes, & Nelson, 1984; Barlow & Hersen, 1984; Johnston & Pennypacker,

1993; Kazdin, 1982; Sidman, 1960), which include almost all treatment procedures used

in communicative disorders (Hegde, 2003). McReynolds and Kearns (1983) described

single-subject research as applied research that has direct clinical application. These

authors go on to state that a potential benefit of increased use of this approach is related

to the issue of accountability and establishing treatment efficacy. Likewise, Mertens

(2005) emphasized the value of single-case designs for testing the effectiveness of a

specific instructional strategy or a therapeutic technique on behaviors.

Bordens and Abbott (2008) stated that a single-subject approach does not depend

on averaging across subjects to control the effects of random factors (such as is needed in

31 31

group designs); therefore, it can be used with only a few subjects. The controls are built

into the design in such a way that a control group is not utilized and a large number of

subjects are not needed. With a multiple baseline across participants design, the

independent variable (treatment using VFEs) is manipulated at specific points in time to

show that the dependent variables (maximum phonation time, maximum phonation

frequency range, jitter, and shimmer) change when and only when the treatment is

applied. In this way, the multiple baseline design can provide strong empirical evidence

regarding the effectiveness of VFEs for enhancing the voices of trained vocal performers.

Data were statistically analyzed using Busk and Serlin’s (1992) d statistic which

measures the effect size for single-subject designs. Effect size refers to the association

between two variables, which in this case was between baseline and treatment, baseline

and maintenance, and treatment and maintenance. Additionally, visual inspection of the

graphs was completed for a thorough analysis of the data collected.

Participants

This research study consisted of three adult male participants who were healthy

trained singers. These participants were recruited through non-randomized self-selection

from the Fresno State Music Department. Each participant was enrolled in school for the

semesters of Fall 2017 and Spring 2018 as well as enrolled in voice lessons with a Fresno

State music professor; therefore, the study was conducted during this time.

The inclusion criteria stated that all participants had to be (a) male, (b) between

the ages of 18-30 years, (c) trained singers from the Fresno State Music Department, (d)

able to pass a hearing screening, and (e) willing to participate in VFEs twice a day, two

times each. Exclusion criteria included (a) the presence of known laryngeal pathologies

or voice disorders and (b) smoking. The inclusion and exclusion criteria were determined

through the participants’ responses to a questionnaire (Appendix A) and the results of a

32 32

hearing screening (Appendix B) administered at 25 dB for 500, 1K, 2K, and 4K Hz in

both ears.

Setting

The consent meeting and all sessions (baseline, treatment, and maintenance) were

conducted in the Professional Human Services (PHS) Building, Room 217. The room

consisted of two chairs where the researcher and participant sat next to each other in front

of the Computerized Speech Lab (CSL) (Model 4500b) which was equipped with a

speaker and microphone. The room also contained 15 desks for classroom purposes and a

videostroboscopy unit for conducting endoscopic laryngeal exams.

Procedures

The participants were selected on a volunteer basis. The researcher distributed

information fliers (see Appendix C) to a faculty member in the Fresno State Music

Department. These fliers were made available to students who were enrolled in voice

lessons with a professor of the Music Department for the Fall 2017 and Spring 2018

semesters. The students who were interested in being a part of the study or desired more

information, contacted the researcher or the faculty member of the Music Department,

using the contact information provided on the flier.

Once the participants expressed their interest in participating in the study and

requested more information, the researcher answered any questions the participants had

regarding the study. If the participants were still interested in participating then the

researcher asked a series of questions via email (see Appendix A) to determine if they

met the participation criteria. If the potential participant did not meet the inclusion

criteria, he was then thanked for his interest in the study and excused from participation.

For this study, one potential participant did not meet the criteria. He was thanked for his

interest and excused from participation. Once it was determined that the remaining

33 33

potential participants met criteria, an in person meeting was scheduled to obtain consent.

During an in person meeting, the researcher read through the consent form with the

potential participant (see Appendix D) and addressed any concerns or questions they had.

Hearing Screening

Once informed consent was obtained, the researcher conducted a hearing

screening for each participant with supervision by a licensed and certified speech-

language pathologist. The researcher explained to the participants the procedure for the

hearing screening and answered any questions. The researcher presented a tone at 50dB

for 1000 Hz to ensure the participant understood what was expected. If the tone was

heard and the instructions were understood, the hearing screening continued at 25dB for

500, 1000, 2000, and 4000 Hz in both the right ear and left ear. Each of the participants

who met criteria, also passed the hearing screening.

Equipment

During each phase, two programs on the CSL (KayPENTAX, 2011a, 2011b) were

used for acoustic measurements of the participants’ voices. The Real Time Pitch program

(KayPENTAX, 2011b) was used to measure maximum phonation frequency range and

maximum phonation time. The Multidimensional Voice Program (MDVP)

(KayPENTAX, 2011a) measured jitter and shimmer. The participants were seated 5 cm

away from the microphone which was connected to the computer during all

measurements. The Pitch Analyzer Application on the iPhone was used to measure

consistency across each trial in regards to dB levels for all trials and frequency levels for

maximum phonation time, jitter, and shimmer trials. The participants were required to

maintain a dB level that was no more +/- 5dB and a musical note +/- 1 half step (a

semitone) from the previous trials.

34 34

Baseline Phase

Prior to initiating treatment, baseline measures were conducted to establish

baseline stability for the dependent variables. Baseline measures were conducted for

maximum phonation frequency range, maximum phonation time, jitter, and shimmer.

Maximum phonation frequency range. For maximum phonation frequency ranges

(MPFR), the Real Time Pitch - Pitch Range Protocol (KayPENTAX, 2011b) was used to

measure the lowest and highest frequencies performed by the participants, as stated in the

Pitch Range Protocol. The Pitch Range Protocol instructions appeared on the computer

screen prior to each trial as a visual reminder to the participants. Each trial was performed

into the microphone which connected to the CSL program. To obtain measurements, the

participants were asked to glide from a comfortable midrange note to his highest note on

an /a/. Next, each participant glided from a comfortable midrange note to his lowest note

on an /a/. The participants were given three attempts to complete the two tasks to ensure

reliability. During each trial, the participants were required to perform the task without

glottal fry or aspirate attacks. If the researcher noticed glottal fry or aspirate attacks, the

trial was discontinued, and the participant was instructed to perform the trial again

without glottal fry or aspirate attacks. The CSL provided data in terms of maximum pitch,

minimum pitch, and pitch range for each individual trial. The researcher used the highest

pitch range of the three attempts as the baseline MPFR. Baseline stability for MPFR was

defined as being within +/- 10 Hz across 2 consecutive sessions.

Maximum phonation time. In regards to maximum phonation time (MPT), the

Real Time Pitch - MPT Protocol (KayPENTAX, 2011b) was utilized to measure the

longest duration of a single vowel produced by the participant. The MPT Protocol

instructions appeared on the computer screen prior to each trial as a visual reminder to

the participants. The participants were instructed to take a deep breath and hold an /a/ for

35 35

as long as possible on a comfortable note of their choice. The participants were also

instructed to discontinue the task prior to using residual air. The participants were given

three tries to complete the task to ensure reliability. The researcher used the longest

duration out of the three attempts as the baseline MPT. Baseline stability for MPT was

defined as being within +/- 2 seconds across 2 consecutive sessions.

Jitter and shimmer. Jitter and shimmer measurements were taken using the MDVP

(KayPENTAX, 2011a). Jitter is a measurement of cycle-to-cycle variations in the

frequency of vocal fold vibrations and is therefore a reflection of pitch stability in the

participant’s voice. Shimmer is a measurement of cycle-to-cycle variations in the

amplitude of the vocal fold vibrations and also reflects the stability of a participant’s

voice. As described in chapter 1, a low percentage of jitter and shimmer is likely to result

in a voice with better vocal quality and is therefore desirable. The participants were

instructed to hold an /a/ on a comfortable note until the sound bar was complete on the

computer screen and the researcher ended the trial by pressing the “stop” symbol on the

screen or the space bar on the keyboard. The participants were given three tries in order

to allow for the best possible trial and reliability. The researcher used the lowest

percentage recorded for the three trials as the baseline. For jitter and shimmer, baseline

stability was defined as being within +/- 0.5 % across 2 consecutive sessions.

Vocal Function Exercise Program

The VFEs are designed to improve overall vocal function and to increase

laryngeal strength and muscle tone (Stemple et al., 1994). The steps for the exercises are

outlined as follows:

1. Maintain /i/ for as long as possible on a consistent, comfortable note.

2. Glide from the lowest to the highest note on /o/.

3. Glide from the highest note to the lowest note on /o/.

36 36

4. Maintain the musical notes of middle C and D, E and F, and G five notes

above middle C for as long as possible on /o/.

The details for each step is described in the treatment phase below.

Treatment Phase

The procedures in this phase were consistent with VFEs procedure outline in

Stemple et al. (1994). During the initial treatment session, the researcher conducted probe

measurements, utilizing the same procedures described for the baseline measures in order

to ensure reliability. The participants were provided with education regarding what the

VFEs are and the potential vocal benefits associated with them. The researcher then

taught and educated the participants on how to properly perform VFEs. The participants

were given multiple tries to perform VFEs for the researcher and were required to

provide a successful return demonstration of VFEs. They were then required to perform

each of the exercises two times, twice a day on their own. The participants were provided

with a chart (see Appendix E) to keep track of their performance while completing VFEs

each day at home, on their own. The researcher also gave each participant a CD (Stemple,

2006a) and DVD (Stemple, 2006b), recorded by Stemple, that demonstrated how to

properly perform VFEs.

Treatment was conducted for 8 weeks for each of the three participants. During

the treatment phase, the participants met with the researcher once a week to conduct

probe measurements utilizing the same procedures described for the baseline measures.

The researcher also:

1. Verified that the participants were performing VFEs properly, and provided

corrective feedback when needed.

2. Answered any questions and addressed any concerns.

37 37

3. Gave verbal praise for correct productions using a fixed ratio 1 (FR1) schedule.

Reinforcement included statements such as “great job” or “good breath

support.”

The first step was the warm-up exercise. The participants maintained an /i/ sound

for as long as possible on a consistent, comfortable note with a nasal tone (Stemple et al.,

1994). The goal for this exercise was for the participants to breathe from the diaphragm

and maintain the pitch, on a single breath, for at least 10 seconds (Stemple, 2005). The

participants were required to maintain an extremely nasal tone while producing the pitch

(Stemple et al., 1994). Stemple described the nasal tone as “the wicked witch” tone

(Stemple, 2006b). It should be noted that the participants used a straight-tone without

vibrato present. Vibrato is defined as “a fluctuation in a note, vibrating above and below

the fundamental tone to produce increased volume and expression.” (Ashkenazy &

Fabian, 2010, p. 123).

Second, the participants glided from the lowest to the highest note on an /nol/ as

in the word “knoll” while maintaining a lip buzz (Stemple, 2005; Stemple et al.,1994;

Stemple et al., 2014). The word “knoll” helped to create a forward tone focus and assisted

with opening up the pharynx (Stemple et al., 2014). The participants took a deep breath

and glided from the lowest to the highest note with slow control. During this glide, the

participants maintained /nol/ with a lip buzz. Lip buzz was described to the participants

as having tight constricted lips to create a buzz during the production of /nol/. The

participants performed this exercise at least twice. The goal for this exercise was to have

an easy onset of the vocal folds resulting in increased phonation frequency range by at

least one whole step with no pitch breaks (Stemple, 2005). Pitch breaks are common in

this exercise due to the passagio of a singer’s voice. The passagio is the transition period

between two voice registers. In males, it is typically the transition between the chest

voice which presents a lower frequency and the falsetto which presents a higher

38 38

frequency. These pitch breaks can occur involuntarily if the singer does not have the

muscular strength to transfer the muscle control from the thyroarytenoid muscle to the

cricothryroid muscle (Willis & Kenny, 2011). Pitch breaks in the passagio can also occur

from age and insufficient breath support.

In contrast, the participants performed the third exercise by gliding from the

highest note to the lowest note on an /nol/ as in the word “knoll” while maintaining a lip

buzz (Stemple, 2005; Stemple et al.,1994; Stemple et al., 2014). The participants took a

deep breath and glided from their highest to their lowest notes in a controlled manner,

while maintaining the lip buzz on /nol/. The goal for this exercise was to have an easy

onset of the vocal folds and no pitch breaks (Stemple, 2005). Pitch breaks in the passagio

are less common in this exercise because the muscle strength is reversed. Singers find it

easier to glide from a high pitch to a low pitch.

Finally, the participants maintained the musical notes of middle C, D, E, F, and G

five notes above middle C, for as long as possible on /ol/ as in the word “old” without the

ending consonant /d/, while maintaining a lip buzz (Stemple, 2005; Stemple et al.,1994;

Stemple et al., 2014). The participants were instructed to take a deep breath and focus the

sound, with the lip buzz, for proper execution of this exercise. The goal for this exercise

was for the participants to breathe from the diaphragm and maintain the note, on a single

breath, for at least 10 seconds.

Maintenance Phase

Stemple’s VFE program is designed to be a 6 to 8 week program (Stemple, 2005).

After 8 weeks of treatment was completed, the participants were instructed to discontinue

performing VFEs until the final maintenance probe measures were conducted. VFEs were

discontinued in order to determine if the participants maintained improvement without

treatment. Maintenance probe measures were collected 1 week after and 30 days after the

39 39

final treatment session. During this phase, the researcher conducted the maintenance

probe measurements utilizing the same procedures described for the baseline measures.

Reliability

Reliability was established by using the CSL program to gather the data.

According to the CSL, “Its precise sampling rates ensure no alteration of the signal

during capture. This allows measuring of even the smallest amount of noise or

perturbation in the voice, which is critical for accurate and repeatable results”

(Computerized Speech Lab [CSL], 2018, para. 2). In addition, the microphone attached to

the CSL was placed at an appropriate distance from the participant during measurements,

and the distance was consistently maintained throughout subsequent sessions. Also,

background noise was limited by ensuring the door to the treatment room was closed for

all measurements.

Data Analysis

Data were analyzed by visual inspection of the graphs for each vocal

measurement regarding baseline, treatment, and maintenance phases. Graphs displaying

the data for each phase were inspected to determine whether there was a treatment effect.

In other words, inspection of the graphs was completed to determine if the dependent

variables (MPFR, MPT, jitter, and shimmer) changed in response to introducing the

independent variables (treatment with VFEs). Visual inspection was also used to

determine whether any treatment effect was maintained after treatment was discontinued

and to confirm baseline stability.

Additionally, statistical analysis was conducted using Busk and Serlin’s (1992) d

statistic which is considered an appropriate measurement for single-subject designs. This

statistic was utilized to determine the effect size between baseline and treatment, baseline

and maintenance, and treatment and maintenance outcomes. The effect size refers to the

40 40

relationship between the variables previously listed. Its purpose is to determine if there

was a great difference between the baseline, treatment, and maintenance phase to account

for any improvement in MPFR, MPT, jitter, and shimmer.

CHAPTER 4: RESULTS

Throughout the study, participants were required to produce three trials for each

of the vocal measures being assessed: MPT, MPFR, jitter, and shimmer. Data analysis

was based on the participants’ best performance across those three trials. Data were

analyzed by visual inspection of the graphs for each vocal measurement regarding

baseline, treatment, and maintenance phases. Graphs displaying the data for each phase

were inspected to determine whether there was a treatment effect. In other words,

inspection of the graphs was completed to determine if the dependent variables (MPFR,

MPT, jitter, and shimmer) changed in response to introducing the independent variables

(treatment with VFEs). Visual inspection was also used to determine whether any

treatment effect was maintained after treatment was discontinued and to confirm baseline

stability.

Additionally, data were statistically analyzed using Busk and Serlin’s (1992) d

statistic in order to determine the effect size between the respective phases. This statistic

was used to determine the effect size between the treatment vs baseline measures (t vs b),

maintenance vs baseline measures (m vs b), and maintenance vs treatment measures (m

vs t). The effect size is an indicator of the relationship between the three phases and was

used to evaluate any improvement noted in the dependent variables. Busk and Serlin’s

(1992) d statistic was measured using the following equation:

A2 indicated either the treatment or maintenance phase when compared to A1, which

specified either the baseline or treatment phase, respectively, depending on which phases

were being compared. 𝑋 referred to the mean, or the average. SA1 referred to the standard

deviation of the A1 data.

42 42

Maximum Phonation Frequency Range

Figure 1 shows MPFR as a function of session for each participant. Baseline

stability was established across sessions 2 and 3 for participant 1 and sessions 1 and 2 for

participant 2 and 3. Visual inspection of the data for participants 2 and 3 show a desired

treatment effect in that MPFR increased when the intervention was applied. In addition

frequency ranges for the participants who were not treated remained stable until such

time as their treatment began. In other words, the dependent variable (MPFR) changed

only when the independent variable (VFEs) was introduced. Figure 1 suggests that

participant 2 increased by 34.12 Hz which is about 2 semitones, or 1 whole step in

musical notes for a singer. However, participant 3 increased by 84.22 Hz, which is about

8 semitones, or 4 whole steps, and a significant increase for a trained singer. In addition,

participants 2 and 3 maintained the treatment effect after VFEs were discontinued. This

treatment effect was not apparent for participant 1 as his treatment data remained

consistent with his baseline throughout the course of the study. Possible reasoning for this

will be discussed in Chapter 5. Figure 1 suggests that participant 1 increased by 11.82 Hz

which does not reveal a statistically significant increase in MPFR. Even though

participant 1 only demonstrated minimal improvement, he also maintained his MPFR

after VFEs were concluded.

Table 1 shows Busk and Serlin’s (1992) d statistic results for all three

participants. All three participants demonstrated improvement in their MPFR when

comparing baseline and treatment phase measures, although the improvements for

participant 1 did not reach statistical significance with an effect size of 0.33. According to

Table 1, participants 2 and 3 demonstrated statistically significant improvement from the

baseline to the treatment phase with an effect size of 8.76 and 3.87, respectively. Table 1

also shows a significant increase in MPFR for participants 2 and 3 when comparing the

maintenance phase and baseline phase with an effect size of 10.42 and 9.39, respectively.

43 43

Figure 1. Maximum phonation frequency range across participants

44 44

Table 1

Busk and Serlin’s (1992) d Statistic (Maximum Phonation Frequency Range)

Phases Participant 1 Participant 2 Participant 3

t vs b 0.33 8.76 3.87

m vs b 0.64 10.42 9.39

m vs t 0.51 0.27 1.23

Maximum Phonation Time

Figure 2 shows MPT as a function of session for each participant. Baseline

stability was established across sessions 1 and 2 for participants 1 and 2, and sessions 2

and 3 for participant 3. Visual inspection of the data for participants 1 and 2 show a

desired treatment effect in that the MPT increased when the intervention was applied.

The MPT for the participants who were not treated remained stable until such time as

their treatment began. In other words, the dependent variable (MPT) changed only when

the independent variable (VFEs) was introduced. Figure 2 suggests that participant 1

increased by 9.5 seconds which revealed a significant increase in the desired treatment

effect for MPT. Participant 2 increased by 4.37 seconds and furthermore by 2.68 seconds

from his treatment to his maintenance phase. In addition, participants 1 and 2 maintained

the treatment effect after VFEs were discontinued. After the first week of treatment was

initiated for participant 3, a significant increase in MPT was demonstrated; however, his

treatment data decreased during subsequent treatment sessions as compared to his

baseline. Reasoning for this will be discussed in Chapter 5. Participant 3 maintained the

decrease in treatment data after VFEs were concluded.

Table 2 shows Busk and Serlin’s (1992) d statistic results for all 3 participants for

MPT. Participants 1 and 2 demonstrated improvement in their MPT when comparing

45 45

Figure 2. Maximum phonation time across participants

46 46

baseline and treatment phase measures. Participants 1 and 2 demonstrated statistically

significant improvement from the baseline to the treatment phase with an effect size of

6.72 and 3.17, respectively. Table 2 also shows a significant increase in MPT for

participants 1 and 2 when comparing the maintenance phase and baseline phase with an

effect size of 8.16 and 5.18, respectively. This demonstrates that participants 1 and 2

maintained and even improved upon their treatment results. However, participant 3

demonstrated a decrease in MPT with an effect size of -3.11 when comparing the

treatment and baseline phases. He also demonstrated an effect size of -4.35 when

comparing the maintenance and baseline phases.

Table 2

Busk and Serlin’s (1992) d Statistic (Maximum Phonation Time)

Phases Participant 1 Participant 2 Participant 3

t vs b 6.72 3.17 -3.11

m vs b 8.16 5.18 -4.53

m vs t 0.82 1.04 -0.38

Jitter

Figure 3 shows jitter as a function of session for each participant. Baseline

stability was established across sessions 2 and 3 for all participants. Visual inspection of

the data for participant 1 showed a desired treatment effect in that jitter decreased when

the intervention was applied. The jitter percentage for the participants who were not

treated remained stable until such time as their treatment began. In other words, the

dependent variable (jitter) changed only when the independent variable (VFEs) was

introduced. Figure 3 suggests that participant 1 decreased by 1.177% which reveals a

significant decrease of jitter for a trained singer. In addition, participant 1 maintained the

treatment effect after VFEs were discontinued. This treatment effect was not confirmed

47 47

for participant 2 as his treatment data remained consistent with his baseline throughout

the treatment and maintenance phases. Participant 2 decreased by 0.055% which is not a

significant decrease of jitter. Additionally, the treatment effect was not observed in

participant 3 as his treatment data inconsistently increased and decreased throughout the

course of the study. Possible reasoning for this will be discussed in Chapter 5. Even

though participant 3 did not demonstrate improvement or maintenance of jitter after

VFEs were concluded, the percentage of jitter remained a low percentage that is adequate

for vocal use.

Table 3 shows Busk and Serlin’s (1992) d statistic results for all three participants

for jitter. Participants 1 and 2 demonstrated improvement in their jitter when comparing

baseline and treatment phase measures. Participants 1 and 2 demonstrated statistically

significant improvement from the baseline to the treatment phase with an effect size of -

0.87 and -3.40 respectively. Additionally, Table 3 also shows a significant decrease for

participant 1 between the maintenance and baseline phases with an effect size of -0.80.

Furthermore, participant 3 demonstrated a slight and insignificant increase in jitter when

comparing the treatment and baseline phases with an effect size of 0.12. He also

demonstrated an effect size of -4.35 when comparing the maintenance and baseline

phases.

Shimmer

Figure 4 shows shimmer as a function of session for each participant. Baseline

stability was established across sessions 1 and 2 for participant 1 and 3 and sessions 2 and

3 for participant 2. Visual inspection of the data for participant 3 showed a desired

treatment effect in that shimmer decreased when the intervention was applied. The

shimmer percentage for the participants who were not treated remained stable until such

time as their treatment began. In other words, the dependent variable (shimmer) changed

48 48

Figure 3. Jitter across participants

49 49

Table 3

Busk and Serlin’s (1992) d Statistic (Jitter)

Phases Participant 1 Participant 2 Participant 3

t vs b -0.87 -3.40 0.12

m vs b -0.80 5.49 2.33

m vs t 0.33 3.01 1.54

only when the independent variable (VFEs) was introduced. Figure 4 suggests that

participant 3 decreased by 0.502% during treatment with VFEs. Participant 3 did not

maintain the treatment effect as demonstrated in his 30-day maintenance session. Possible

reasoning for these results will be discussed in Chapter 5. This treatment effect was not

apparent for participant 2 as his treatment data remained consistent with his baseline

throughout the course of the study. Participant 2 maintained his already established

shimmer percentage after completion of VFEs. Additionally, the treatment effect was not

observed for participant 1 as his treatment data inconsistently increased and decreased

throughout the course of the study. Participant 1 remained variable after completion of

VFEs, however maintained an adequate shimmer percentage for vocal production.

Table 4 shows Busk and Serlin’s (1992) d statistic results for all 3 participants for

shimmer. Statistically, participants 1 and 3 demonstrated improvement in their shimmer

when comparing treatment and baseline measures with an effect size of -0.60 and -0.31,

respectively. For participants 1 and 3, a decrease of shimmer was not observed from

baseline to maintenance phases or from treatment to maintenance phases. Table 4 shows

these results as an effect size of 0.64 and 0.57 for participant 1 and 1.07 and 0.59 for

participant 3, respectively. Participant 2 did not demonstrate a decrease in shimmer from

baseline to treatment phases with an effect size of 1.29. However, improvement was

shown from the maintenance and baseline phases and maintenance and treatment phases

with an effect size of -0.57 and -1.21, respectively.

50 50

Figure 4. Shimmer across participants

51 51

Table 4

Busk and Serlin’s (1992) d Statistic (Shimmer)

Phases Participant 1 Participant 2 Participant 3

t vs b -0.60 1.29 -0.31

m vs b 0.64 -0.57 1.07

m vs t 0.57 -1.21 0.59

CHAPTER 5: DISCUSSION

The current study evaluated the effects of Stemple’s VFEs on various vocal

measurements (MPT, MPFR, jitter, and shimmer) with trained male adult singers. The

results of this study indicate that VFEs are exercises that could be utilized to enhance the

trained singing voice in respect to MPT and MPFR. The research hypotheses for this

study were:

1. Participants who perform VFEs correctly two times, twice a day for 8 weeks,

will significantly increase their maximum phonation frequency and maximum

phonation time.

2. Participants who perform VFEs correctly two times, twice a day for 8 weeks,

will significantly decrease their jitter and shimmer.

The overall results of the study indicated that VFEs are a treatment technique that

could enhance various measures of the normal voice, particularly in the trained singer. A

trained singer is assumed to have the foundation for a healthy singing voice and proper

technique. VFEs are meant to improve the vocal quality of disordered voices. However,

previous research conducted with trained singers, although limited, suggested that VFEs

also enhance an already established trained voice. The results of this study contributed to

the evidence base in this area.

The first hypothesis stated that participants who performed VFEs correctly two

times, twice a day for 8 weeks, would significantly increase their maximum phonation

frequency and maximum phonation time. This hypothesis was supported through the

results of the current study. In regards to MPFR, visual inspection of the data for

participants 2 and 3 showed a desired treatment effect in that MPFR increased when the

intervention was applied. This treatment effect was not apparent for participant 1 as his

treatment data remained consistent with his baseline throughout the course of the study.

53 53

This lack of treatment effect is thought to be due to the fact that participant 1 had the

most substantial vocal training experience prior to the study. Because of this, he started

with a baseline MPFR that was already over 300Hz, which would be considered a

substantial range. Therefore, he had less room for improvement. With the use of Busk

and Serlin’s (1992) d statistic, all 3 participants showed improvement in their MPFR

when comparing baseline and treatment phase measures, although the improvements for

participant 1 did not reach statistical significance. In addition, we see that all participants

maintained any improvement noted after VFEs were completed.

Although most studies reviewed did not observe a significant increase in MPFR,

it is important to note the studies that demonstrated significant improvement. Ellis and

Beltyukova (2011) noted a significant increase in MPFR in normal voices who were

monitored during VFEs. They found that MPFR increased after only 4 weeks of

performing VFEs, which is considered significant for a normal voice. Tay et al. (2012)

noted an increase in MPFR for aging choral singers. It was suspected that this increase

occurred due to the contracting and stretching exercises included in VFEs. The results of

this study further support the benefits of VFEs for expanding the MPFR in trained singers

whose MPFR is below 300 Hz.

For MPT, visual inspection of the data for participants 1 and 2 showed a desired

treatment effect in that MPT increased when the intervention was applied. After the first

week of treatment was initiated for participant 3, a significant increase in MPT was

demonstrated; however, his treatment data decreased during subsequent treatment

sessions as compared to his baseline. Prior to baselines, participant 3 was performing

breathing exercises each day to increase his breath support for singing. All participants

were instructed to continue their vocal routines that were present prior to the study.

Nonetheless, during treatment, participant 3 had to discontinue performing the breathing

exercises due to some unexpected circumstances. At that time he moved into a new living

54 54

situation that exposed him to environmental mold and poor air quality. As a result, he

discontinued his breathing exercises and at that time a decrease in MPT was noted. As a

result, the data revealed a longer MPT during the baseline phase as opposed to the

treatment phase for participant 3.

In respect to Busk and Serlin’s (1992) d statistic, participants 1 and 2

demonstrated a statistically significant improvement as seen in the increase in their MPT

when comparing baseline and treatment phase measures. However, participant 3

demonstrated a decrease in MPT when comparing the treatment and baseline phases.

Participant 3 maintained the decrease in treatment data after VFEs were concluded.

However, participants 1 and 2 maintained the desired treatment effect throughout the

maintenance phase.

The results for MPT were congruent with the findings of several research studies

reviewed (Ellis & Beltyukova, 2011; Gorman et al., 2008; Kaneko et al., 2012; Sabol et

al., 1995). Sabol et al. (1995) found that the increase of MPT in singers was even more

significant than for non-singers. This suggested that the establishment of the technique

and education already present in the trained singer could assist with a significant increase

in MPT when paired with VFEs. Additionally, Kaneko et al. (2012) suggested that MPT

increased due to the adductory power exercise performed in VFEs in which the goal was

to increase respiration and endurance. Overall, the results of this study contributed to

evidence regarding the potential benefits of VFEs.

The second hypothesis stated that participants, who performed VFEs correctly

two times, twice a day for 8 weeks, would significantly decrease their jitter and shimmer.

This hypothesis was not supported by the results of this study. Visual inspection of the

data for participant 1 initially showed a desired treatment effect in that jitter decreased

when the intervention was applied, however the amount of improvement was minimal.

Participant 1 maintained this treatment effect at the 1-week maintenance probe, but not at

55 55

the 30 day maintenance probe. Visual inspection of the data for participant 2 also showed

a minimal decrease in percent jitter when the treatment was applied. Overall, his

treatment data remained relatively consistent with his baseline throughout the treatment

and maintenance phases. Additionally, visual inspection of the data for participant 3

revealed treatment data that inconsistently increased and decreased throughout the course

of the study.

Busk and Serlin’s (1992) d statistic demonstrated an improvement (reduction) of

jitter for participants 1 and 2 when comparing baseline and treatment phase measures;

however, this improvement did not reach the level of statistical significance.

Furthermore, participant 3 demonstrated a slight yet clinically insignificant increase in

jitter when comparing the treatment and baseline phases. Even though participant 3 did

not demonstrate improvement during the treatment phase, or maintenance of jitter after

VFEs were concluded, the percentage of jitter remained low overall and within a range

considered appropriate for a healthy voice.

All of the participants were well below the threshold for acceptable jitter (less

than 1.04%) (KayPENTAX, 2011a) at their baseline measures. Therefore, there was not a

need for further reduction and little to no room for improvement. Second, it should be

noted that jitter was difficult to measure due to the sensitivity of the CSL program. The

CSL would pick up the slightest overtones of the participants’ voices, and therefore

significant variability was noted across sessions. Finally, the results may reveal that VFEs

simply are not effective in reducing jitter in trained singers with healthy voices.

For shimmer, visual inspection of the data revealed a desired treatment effect only

for participant 3. For participant 3, shimmer decreased when the intervention was

applied. However, participant 3 did not maintain this treatment effect once VFEs were

discontinued, as demonstrated in his 30-day maintenance probe. Visual inspection of the

data did not reveal a desired treatment effect for participants 1 or 2. The treatment data

56 56

for participant 2 remained consistent with his baseline throughout the course of the study.

Additionally, the treatment data for participant 1 inconsistently increased and decreased

throughout the course of the study. Utilization of Busk and Serlin’s (1992) d statistic

showed improvement (a reduction) of shimmer for participants 1 and 3 when comparing

treatment and baseline measures; however, this improvement did not reach the level of

statistical significance. The statistical analysis confirmed that participant 2 did not

demonstrate a decrease in shimmer from baseline to treatment phases.

Several possible explanations for these data should be considered. First, as

previously reported for jitter, all of the participants were well below the acceptable

threshold for percent shimmer (no more than 3.810%) (KayPENTAX, 2011a) at their

baseline measures. Consequently, there was not a need for further reduction and little

room for improvement. Second, the sensitivity of the CSL equipment resulted in

significant variation across trials, as noted previously for jitter. Another explanation for

variability could be the vocal changes the participants experienced throughout the day or

the amount of vocal use that was present prior to the sessions. Third, the results may

reveal that VFEs simply are not effective in reducing shimmer in trained singers with

healthy voices. A final observation regarding the results for jitter and shimmer is that

participant 1 and 2 had more extensive vocal training and experience than participant 3,

and thus their baseline measures started off lower, with less variability on subsequent

measures.

The literature review revealed limited research regarding the effects of VFEs on

jitter and shimmer. Tay et al. (2012) noted a significant decrease in jitter and shimmer for

aging choral singers. These authors suggested that an increase in vibratory patterns

influenced the increase of MPFR which directly correlated with the decrease in jitter.

Kaneko et al. (2015) also observed a decrease in jitter as it pertained to individuals with

vocal fold atrophy. No further research studies revealed a decrease in shimmer or jitter

57 57

secondary to performing VFEs. In previously reviewed studies, the participants who

demonstrated a decrease in jitter or shimmer were noted to have a voice disorder present;

whereas, the participants in the current study had healthy, well trained voices prior to

treatment. Therefore, there was little-to-no room for improvement regarding reductions in

jitter and shimmer. It might be interesting to study the effects VFEs might have on jitter

and shimmer in trained vocal performers who were experiencing voice problems at the

time.

In regards to qualitative data, two participants reported to the researcher that they

felt an overall increase in their phonation time when performing. They stated that they

were able to sustain longer lines of music while singing and therefore changed their

breathing patterns with their learned songs. All participants reported that they felt their

overall singing quality was healthier and less fatigued while singing in multiple

performances. They reported that VFEs enhanced their foundation for singing and

provided them with more breath support, which is one of the most important aspect of

singing.

Limitations

The present research study had several limitations, which may have affected the

study’s external or internal validity. These limitations should be contemplated prior to

evaluating VFEs with trained singers.

Generality

External validity could have been affected in this research study due to the small

sample size with the multiple baseline across participants research design. Sample size is

a potential threat to external validity since there were only three participants in the study.

The multiple baseline across participants design controls for many outside variables and

is intended for a small number of participants in order to control the treatment variability.

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However, the small sample size may hinder the ability to transfer the findings of the

study to all male trained singers. Since the target population was limited and the length of

the VFEs program lasted 8 weeks, having a smaller sample size was ideal; however, this

is not always favorable for generalization of the results. The logical generalization of the

findings may not apply to other singers and different voice types.

In order to obtain generality, the researcher should be able to extend the results to

different situations, individuals, researchers, and settings (Hegde, 2003). The participants

for this research study were similar in age, same gender, and were from the same music

program. These aspects in itself do not allow for a generalization across a population. A

multiple baseline across participants design does not always allow itself to generalization

due to the nature of the design and similarity of the participants in order to demonstrate

control. However, it can be argued that a multiple baseline research design allows for

generality by distributing the treatment across the participants for subsequent

observations. In retrospect, the distribution of treatment can lend itself to generalization

across a population.

Environmental Factors

Every singer has vocal issues from time to time due to illness, swelling of the

muscles, respiratory issues, vocal fatigue, or inadequate vocal quality. Each participant

demonstrated at least one of these factors in one or a few of the sessions. Participant 1

and 2 experienced vocal fatigue due to high demand of singing in the music department.

Prior to conducting the study, participant 3 was practicing breathing exercises to help

increase his overall lung capacity. All participants were instructed to continue their vocal

regime to not skew results of the study. However, during the treatment phase, participant

3 demonstrated respiratory issues due to environmental changes he experienced. He

reported moving to another location during the study, which was not conducive for

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healthy breathing. Ultimately, this resulted in discontinuation of his breathing exercises

as part of his vocal regime. Therefore, the results of his MPT may have been skewed.

History

The program for VFEs is an 8-week program in which the participants perform

the exercises twice a day, two times each. This can be tedious and time consuming for the

participants involved. Since the participants were not monitored each time VFEs were

performed, they could have become uninterested and not performed the exercises to their

full potential. This could have led to false data and unreliable results for the study.

Additionally, the participants were required to track their practice on a chart provided to

them. The participants claimed to report honestly and accurately; however, without the

researcher monitoring each practice session, it is unclear if they followed through on

performing the exercises consistently.

Moreover, the participants were taking classes, singing in performances, working,

and going about their everyday activities. The participants may not have been able to set

aside enough time on some days for VFEs to be performed and may have been fatigued

from their daily activities. This could have possibly affected vocal function during

performances of VFEs and may have affected the overall results during treatment

sessions.

Testing

Another threat to internal validity could have been the testing procedures due to

multiple data collections during the baseline, treatment, and maintenance phases. Since

each variable was measured more than once, reactive measures, or changes in the

variables due to repeated testing, may have influenced the results of the study (Hegde,

2003).

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Measurements were taken utilizing the same protocols for each session when

collecting data. The participants were provided practice trials in order to fully understand

the task during the sessions. The intention of the practice trials was to assist the

participant in gaining more confidence to perform the measure to the best of their vocal

ability. As the study continued, the participants became more familiar with the tasks

required while taking measurements. Therefore, the results could have improved due to

familiarity of the testing protocol and required tasks during the baseline, treatment, and

maintenance phases.

Recommendations

Several specific recommendations are suggested for replication of the present

study and for future research on this topic. It is recommended to have a larger sample size

in order to generalize the results to a broader population. Obtaining more participants

with a multiple baseline across participants design could be difficult to manage; however,

this would be necessary for generality to other singers and voice types. Another option

would be to study this issue using many more participants in a control group design.

A second recommendation would be to have more regulation over the participants

in regards to practicing VFEs on their own. Ellis and Beltyukova (2011) monitored the

participants’ practice regime while performing VFEs, which demonstrated significant

improvement for the monitored group. If participants are aware that they are being

monitored it could result in more accurate and consistent practice of VFEs. Additionally,

the researchers could require that the participants record their entire practice session to

ensure they are consistent with their voice regime outside of VFEs. This could ensure that

any improvement (or not) is coming from VFEs and not a change in their vocal routine.

Moreover, even though this was not a limitation of the current study, the

researchers suggest using multiple vowels to observe if there is any change in the results

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based on producing vowels other than /a/. Singers are trained in proper positioning of

vowels; however, some individuals prefer to sing with different vowels that assist with

increasing their overall vocal technique.

Finally, it is recommended that the study be replicated using participants who are

trained vocal performers experiencing voice problems. The results of previous research

combined with the results of this study suggest that VFEs might have the potential to

decrease jitter and shimmer in individuals with voice disorders but not in individuals who

already have healthy voices. Similarly, the research suggests that VFEs might be more

beneficial in improving MPFR when the existing range is below 300 Hz.

Conclusion

Overall, the results of the study partially supported the first hypothesis which

states that participants who perform VFEs correctly two times, twice a day for 8 weeks,

will significantly increase their maximum phonation frequency and maximum phonation

time. The data demonstrated a statistically significant increase in MPFR for participants

2 and 3 following their participation in Stemple’s VFE program. Furthermore, both

participants maintained their improvement throughout the maintenance phase of the

study. In addition, the data demonstrated a statistically significant increase in MPT for

participants 1 and 2 following their participation in Stemple’s VFE program. These

participants also maintained their improvement throughout the maintenance phase of the

study. Generally, the vocal measure that demonstrated the most significant improvement

following implementation of the VFE program was MPT. This finding is consistent with

the results of previous research.

The results of the current study did not support the second hypothesis which

stated that participants who perform VFEs correctly two times, twice a day for 8 weeks,

will significantly decrease their jitter and shimmer. None of the participants experienced

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a statistically significant change in their percent jitter or percent shimmer following

implementation of the VFE program. This suggests that VFEs may not be effective in

reducing jitter and shimmer in male trained singers with healthy voices.

Despite a number of limitations discussed previously, a number of additional

conclusions may be drawn from this study:

1. VFEs may enhance the overall vocal quality of trained singers with previously

established skills,

2. trained singers may have the potential to increase their MPT through the use of

VFEs, and

3. trained singers might benefit from incorporating VFEs into their vocal regime

in order to help establish and maintain a healthy voice.

Finally, it should be noted that this current study was a combined effort among

the Department of Communicative Sciences and Deaf Studies and the Department of

Music at California State University, Fresno. In the field of speech-language pathology,

interpersonal communication and interprofessional collaboration are a significant part of

the job and are critical when conducting research that spans across multiple disciplines.

Therefore, such collaboration is strongly encouraged for any future research on this topic.

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APPENDICES

APPENDIX A: QUESTIONNAIRE

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Hello,

My name is Maelyn De Fede, thank you for your interest in the research study regarding

Dr. Stemple’s Vocal Function Exercises with healthy male singers. For the study, you

would be trained with the vocal exercises, which are short and simple. Then you would

meet with me once a week for about 8-10 weeks to take measurements. You would

practice the exercises on your own everyday at home or school. The study will go into

next semester and would be scheduled around your schedule. If you are still interested,

please let me know if I can answer any other questions or concerns for you.

If you are still interested in participating, please reply to this email with the following

questions answered:

1. Are you between the ages for 18-30 years?

2. Are you a trained singer from the Fresno State Music Department?

3. Would you be willing to do a short hearing screening to assess your general hearing?

4. Do you smoke?

5. Have you ever been diagnosed with a laryngeal pathology by a physician?

6. Have you had any recent concerns regarding your vocal performance?

If you are still interested in participating after answering the questions, we can set up an

in person meeting to talk about the consent form. If it is easier to call me, you may do

that. My number is 559-259-7873. I have also attached the flier regarding the study for

you.

Thank you,

Maelyn De Fede

APPENDIX B: HEARING SCREENING FORM

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APPENDIX C: RECRUITMENT FLIER

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APPENDIX D: CONSENT FORM

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Consent Form

Principal Investigator: Frances Pomaville, Ph.D, CCC-SLP

California State University, Fresno; fpomavil@csufresno.edu

Student Researcher: Maelyn De Fede, B.A.

California State University, Fresno; defede@mail.fresnostate.edu

This study will be conducted by Speech-Language Pathology graduate student, Maelyn De Fede

under the supervision of Dr. Fran Pomaville, Associate Professor in the CSDS Department. This

study will assess the efficacy of Dr. Joseph Stemple’s Vocal Function Exercises (VFEs) in

improving maximum phonational frequency range, maximum phonation time, and jitter and

shimmer in healthy adult trained singers.

If you decide to participate, the study will be conducted in the Speech Science Lab (PHS 217) at

California State University, Fresno during the Spring 2018 semester. Treatment sessions will be

held once a week for 8 weeks, each session will last about 60 minutes. There will be sessions

prior to and after treatment to obtain baseline measurements and final measurements. The

treatment and measurement services will be provided free of charge.

The exercises used in this study are called Vocal Function Exercises (VFEs) created by Joseph

Stemple, PhD, CCC-SLP, ASHAF. The VFEs consist of four different exercises which are

proposed to strengthen and stabilize muscle tone in the larynx to provide an overall improvement

of the voice. The study will consist of:

Learning the VFEs in order to successfully perform them,

Practicing the VFEs everyday two times a day, twice each, at home,

Tracking the at home practices on a chart provided, and

Probe measurements taken during each 60 minute sessions for the following: pitch range,

maximum phonation times, pitch cycles, and loudness cycles.

The VFEs have assisted many people in improving their voice, especially those with voice

disorders. These exercises may help you improve your technique and overall healthy singing

voice. This study can give you more exercises for your repertoire and possibly build upon your

present skills.

As there are benefits, there will be potential risks involved in this study. Risks may include an

imposition on daily life activities and experiencing minor discomfort during the hearing

screening. In order to decrease these risks, the researcher will schedule sessions that are

convenient for you and provide a parking pass, if needed. The researcher will also inform you of

the hearing screening procedures and make it as comfortable as possible.

It is your decision if you would like to participate or not, in this study. If you voluntarily decide to

participate, you may drop out at any time during the study. If you have any questions about the

study please email Dr. Frances Pomaville at the email provided above.

Please sign below if you would like to participate in the research study explained above. Once it

has been turned in, you will receive a copy of this form with your signature.

Participant Signature Date Researcher Signature

APPENDIX E: DAILY PRACTICE CHART

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