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
3 3
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.
7 7
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
20 20
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
21 21
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
23 23
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
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.
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
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
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.
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).
60 60
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
61 61
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
62 62
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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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
75 75
Consent Form
Principal Investigator: Frances Pomaville, Ph.D, CCC-SLP
California State University, Fresno; [email protected]
Student Researcher: Maelyn De Fede, B.A.
California State University, Fresno; [email protected]
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
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