American Institute of Aeronautics and Astronautics

1

Assessment of Crewmember Noise Exposures on the International Space Station

José G. Limardo1 and Christopher S. Allen2 NASA – Johnson Space Center, Houston, Texas, 77058

Richard W. Danielson3 Baylor College of Medicine, Houston, Texas, 77030

Crewmembers onboard the International Space Station (ISS) work and live in a unique workplace environment for a prolonged time period. While on ISS, they are exposed to different noise levels that are produced by onboard equipment, such as fans, exercise equipment, environmental control and life support equipment, and payloads. Noise exposures in ISS pose concerns for human factors and crewmember health risks, such as possible reductions in hearing sensitivity, disruptions of crew sleep, interference with speech intelligibility and voice communications, interference with crew task performance, and reduced alarm audibility. Acoustic dosimeter measurements are conducted onboard ISS every two months and compared to ISS flight rules, in order to assess the acoustic environment to which the crewmembers are exposed, and also to guide recommendations for usage of hearing protective devices. The purpose of this paper is to provide an update on the status of ISS noise exposure monitoring and hearing conservation strategies, as well as to summarize assessments of acoustic dosimeter data collected since Increment 27 (April 2011). Noise exposure levels (sleep, day-time, and 24-hr), LEQ, will be described, as well as the Noise Level Constraint ISS Flight Rule, applications of the Noise Hazard Inventory (NHI), and the Noise Exposure Estimation Tool (NEET). Future directions and recommendations for the ISS noise exposure monitoring program will also be highlighted.

Nomenclature CQ = crew quarter dB = decibel dBA = A-weighted decibel ECLSS = Environmental Control and Life Support System ER = exchange rate GGR&C = Generic Groundrules and Constraints Document HPD = hearing protective device IDRD = Increment Definitions and Requirements Document IMV = inter-module ventilation Inc. = ISS Increment ISS = International Space Station JEM = Japanese Experiment Module JSC = Johnson Space Center LA,24 = 24-hour equivalent noise exposure level LA,PK = highest instantaneous noise level LA,T = noise exposure level, actual crew wear times, T LEQ = equivalent noise exposure level 1 Deputy, Acoustics Office, Habitability and Human Factors Branch, 2101 NASA Parkway/Mail Stop: SF3. 2 Manager, Acoustics Office, Deputy, Environmental Factors Branch, 2101 NASA Parkway/Mail Stop: SF22. 3 Manager for Audiology/Hearing Conservation, Johnson Space Center, 2101 NASA Parkway/Mail Stop: SD3.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

43rd International Conference on Environmental Systems

July 14-18, 2013, Vail, CO

AIAA 2013-3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

2

LEQ8 = equivalent noise exposure level (sleep-time period, 8 hours) LEQ16 = equivalent noise exposure level (work period, 16 hours) LEQ24 = equivalent noise exposure level (full-day, 24 hours) Lmax = highest sampled sound level during the instrument’s run time Lnight = night noise exposure MMOP = Multilateral Medical Operations Panel MORD = Medical Operations Requirements Document MRID = Medical Requirements Integration Document NEET = Noise Exposure Estimation Tool NIOSH = National Institute of Occupational Safety and Health NHI = Noise Hazard Inventory OCA = Orbital Communications Adapter OSHA = Occupational Safety and Health Administration SLM = sound level meter SSC = Space Station Computer TeSS = Temporary Early Sleep Station WHO = World Health Organization

I. Introduction HIS paper presents an update on the status of the International Space Station (ISS) noise exposure monitoring and hearing conservation strategies previously presented1, as well as to summarize assessments of acoustic

dosimeter data collected since April 2011. The strategy includes crew-worn noise exposure monitoring data collected during the work (LEQ16) and sleep (LEQ8) periods on ISS. Details and descriptions of ISS are presented elsewhere1. Crew-worn and environmental monitoring is currently performed by the trained crewmembers onboard ISS, with all technical support provided by ground personnel. Acoustic monitoring measurements were made onboard the ISS in order to assess the acoustic environment to which the crewmembers were exposed. These data were used to ensure a safe working and living environment for the crew, as well as to determine when actions were required in order to reduce the noise onboard the ISS. Requirements are documented in the Medical Operations Requirements Document2 (MORD), the Medical Requirements Integration Document3 (MRID), the Generic Groundrules and Constraints Document4,5 (GGR&C), the Increment Definitions and Requirements Document6 (IDRD) and from the Noise Level Constraint ISS Flight Rule (JSC Flight Rule B13-152).7 The current ISS Noise Level Constraints Flight Rule is based on 24-hour crew-worn noise exposure levels (LA, 24) measured by the ISS acoustic dosimeters. If these levels were 67 dBA or higher, then the crewmembers were required to wear approved hearing protective devices for a predetermined time period according to the Noise Level Constraint ISS Flight Rule. While using this flight rule, there was no indications when (i.e., during which task or activity) the crewmember should don a hearing protective device (HPD). The flight rule’s recommendations only indicated how long the crewmember should have used HPDs during a 24-hour period (without clearly associating to high-noise tasks or activities). In addition, wearing the HPDs at night in the CQs also satisfied the flight rule. As a result, this current flight rule is being revised, to be based on a “task-based” hearing conservation approach, which more clearly identifies when HPDs should be used. More specific details on the revised flight rule will be discussed further in a later section in this paper. Adherence to these guidelines should keep the sound energy levels to which the ear was exposed at an acceptable level. In order to keep continuous background levels low NASA and the Johnson Space Center’s Acoustics Office have developed and implemented acoustic requirements that must be met for hardware and payloads to be certified for spaceflight.8 Acoustic dosimeters are instruments used to measure noise exposure over extended periods of time. A total of three acoustic dosimeters were onboard ISS at all times. The acoustic dosimeter currently used for monitoring ISS noise exposures is a Quest model NoisePro DLX-1®. Detailed explanations on the dosimeter’s features and capabilities are documented in Ref. 1. This instrument was used to obtain two types of acoustic dosimetry measurements. To obtain crew-worn (personal) noise exposure data, the crewmembers wore the acoustic dosimeters for a continuous 24-hour period (including during the sleep-time period), to measure their typical noise exposures as they performed nominal tasks and moved throughout various locations on ISS. The device was stored in a pocket or clipped to the crewmember’s clothing and its microphone was clipped on the crewmember’s collar or lapel so that it was in close proximity to the ear. To obtain static (environmental) noise exposure data at specific fixed locations on

T

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

3

ISS, the acoustic dosimeter was placed in designated, static locations in the ISS, to characterize the internal acoustic environment of ISS, and to assist in the implementation of effective countermeasures to reduce or eliminate crew exposure to high noise levels and the need to don hearing protective devices. Environmental monitoring was one of the key tasks required by all crewmembers onboard ISS in order to ensure a healthy and safe environment. However, because on-orbit crew time was a high demand asset for all operational tasks, acoustic dosimetry monitoring tasks were only scheduled to be performed once every two months. During the monthly acoustic monitoring activity, on the first day, one crewmember would hand out the dosimeters to three crewmembers. Then the crewmember would retrieve the dosimeters the next morning and hand them out to the other three crewmembers for 24-hours. Next the crewmember will deploy them at three fixed ISS locations for static monitoring followed by the data download activity during the fourth day. All crewmembers were trained, prior to flight, in acoustic dosimeter measurement techniques. This training included nominal operation of the acoustic dosimeter hardware, software handling and operational and malfunction procedures, as well as options for HPD use on ISS.

II. Data and Analysis Acoustic dosimetry data were collected from crew-worn and static location measurements. The acoustic

dosimeter activity was divided into four days; (days 1, 2) crew-worn measurements for all six crewmembers, (day 3) static measurements, and (day 4) data download activity. The frequency of these activities was performed every other month. For the crew-worn activity, the crewmember donned the acoustic dosimeter and started the measurement before breakfast during the day of the planned activity. The crew-worn session concluded immediately before post-sleep activities the following day. The crew-worn session included day-time and sleep-time periods (24-hours).

For the static measurement session, the crewmember deployed the acoustic dosimeters at three predetermined

locations during the 3rd day of the acoustic dosimeter activity. The static locations included specific areas in the modules or in the vicinity of specific hardware (e.g., near the treadmill or fans) for conducting assessments and evaluations. These locations were preselected by the Johnson Space Center’s (JSC) Acoustics Office and were rotated throughout the ISS for trending purposes.

After completing the crew-worn and static measurements, the data were then transferred from all three dosimeters to the Space Station Computer (SSC) and downlinked via the Orbital Communications Adapter (OCA). The following paragraphs will discuss the crew-worn and static location measurements, along with the analysis of the data collected during this time period (April 2011 – April 2013).

A. Crew-worn measurement The crewmembers donned acoustic dosimeters before breakfast on the day of the acoustic dosimetry activity for

the duration of 24 hours to record the work-day and sleep period data. The 24-hour equivalent noise exposure levels, LA,24 or LEQ24, given in Table 1 as an example, reflect the actual crew-wear times, T. To date, ISS noise exposure levels have been measured using a 5-dB time-intensity exchange rate (ER)9, consistent with criteria of US occupational standards.

Table 1. Crew-Worn Acoustic Dosimetry Data (Example). LA, T indicates the equivalent noise exposure level during the work and sleep-time periods. LA,PK indicates the highest instantaneous noise level measured during the measurement period.

Activity Acoustic

Dosimeter Serial No.

LA, 24

[dBA] Time Period

Recorded Parameters Hearing Protection

Requirement [hours]

LA, T

[dBA] LA, PK

[dBA] T

[hours:min]

Crew

-Wor

n 1003 69 Work (LEQ, 16) 70.9 121.3 15:25

11 Sleep (LEQ, 8) 54.5 106.8 6:36

1004 68 Work (LEQ, 16) 70.4 123.5 14:14

7 Sleep (LEQ, 8) 51.2 108.6 6:09

1005 66 Work (LEQ, 16) 67.5 135.4 14:58

0 Sleep (LEQ, 8) 55.0 108.0 5:52

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

4

Per recommendations of the Multilateral Medical Operations Panel (MMOP) Acoustics Sub-Group, a 3-dB ER will, in the near future, be used instead of a 5-dB ER, when measuring noise exposures on ISS. A 3-dB increase/decrease represents a doubling or halving of the sound energy, and is based on the equal-energy rule or hypothesis, which assumes that equal amounts of sound energy will produce equal amounts of hearing impairment. The 3-dB ER has been recommended by the US National Institute of Occupational Safety and Health (NIOSH)10 and is used by the US Department of Defense, and has been adopted internationally for use in hearing conservation programs.11 The onboard acoustic dosimeter has the capability for calculating noise exposure using both exchange rates. For reference only until the revised Noise Level Constraint ISS Flight Rule is finally approve, the acoustic dosimetry data will also be reported in the dosimetry reports using the 3-dB equal energy exchange rate. In this paper, all data, including the plots, will be presented using the 5-dB ER unless otherwise stated.

As discussed above, the acoustic dosimeter also has the capability for logging data as a form of time-history of noise levels during the period of measurement. An example of a crew-worn acoustic dosimeter logged data can be seen in Fig. 1. The work-day and sleep-time periods are easily distinguishable from each other. A more challenging task for the authors, however, has been to accurately correlate/match the data logged by the acoustic dosimeter with the crew’s actual tasks and activities; that effort is on-going. In Fig. 1, the cumulative LA,T is plotted against time using both 3-dB (dotted line) and 5-dB (solid line) exchange rates. These logged data provide information with regards to the overall crew noise exposure level. As it can be seen in the graph, several crew tasks/activities were

greater than 80 dBA and one activity was above the hazard limit of 85 dBA, based on the current Noise Level Constraint ISS Flight Rule.7 This particular crewmember was exposed to a noise level of 72 dBA (LEQ24) which (based on the current Noise Level Constraint ISS Flight Rule) required wearing hearing protection for 17 hours. This hearing protection requirement only applied to the crewmember wearing the acoustic dosimeter and the information was obtained after the fact. This illustrates another reason why the flight rules are being updated, since there is no indication when the crewmember should have donned the HPD (only how long the crewmember should have used them).

Figure 1. Crew-worn Acoustic Dosimeter Logged Data. SOURCE: ISS Acoustic Dosimetry Report (March – May 2012), Increments 30/31

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

5

Crew-worn dosimetry data (using 5-dB ER) on ISS has been collected since Increment 1 (see Fig. 2). These data were based on all crewmembers who were a long-duration resident in ISS since November 2001.1 Based on the trend of the data and the current Noise Level Constraint ISS Flight Rule, many crewmembers’ LEQ24 were above 67 dBA, which required use of HPD according to the flight rule. Since Increment 21, more crewmembers’ LEQ24 levels

have been below 67 dBA. This decrease in noise exposure levels was mostly the result of general improvements in acoustic levels on ISS as described in Ref. 12. These improvements include noise mitigation in the Russian Segment (e.g., installation of quiet fans, mufflers, etc.), as well as the addition of new quieter modules (e.g. Columbus Module, Japanese Experiment Module etc.) and crew quarters. However, recent activities and conditions (e.g. clogged fans) in ISS have elevated the noise levels during increments 30 through 32. During ISS increment 33, the acoustic dosimeters malfunctioned and data were not measured. But a work-around crew procedure was developed and measurements were recorded during the following monthly surveys. Until the replacement dosimeters arrive during the summer of 2013, the crewmembers will continue to use the work-around procedures. Noise levels have returned back to nominal levels during increments 34 and 35 after cleaning three IMV fans that were stalled. More details will be discussed further in the paper.

As previously reported, the noise exposure level

for the work period was dependent on where the crewmember spent most of their time.1 The crewmember can work in the Russian segment, the US segment or spend time working equally in both segments (see Fig. 3 for a distribution of LEQ16 during work hours). The data showed that the crewmembers who worked in the Russian segment were exposed to higher noise levels than crewmembers who worked in the US segment. If the data contains any outliers, as seen in Fig. 3, they will be highlighted in the plot. However, work period noise levels (LEQ16) in the US

Figure 2. 24-Hour Crew-worn Dosimetry vs. ISS Increment – using 5-dB ER. SOURCE: ISS Acoustic Dosimetry Report (April – June 2013), Increments 35/36

Figure 3. Distribution of LEQ16 during work hours by location (Increments 1-35) – using 5-dB ER. SOURCE: Acoustic dosimeter data collected on-orbit from November 2001 through April 2013.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

6

segment (increments 27-35) has increased slightly (~2 dBA) as compared to the levels last reported (increments 1-26), while levels in the Russian segment have remained the same (see Figs. 3a and 3b). Use of hearing protection was recommended to crewmembers when working in the Russian Service Module, when exercising on the treadmills (e.g. Node 3), and when exposed to higher noise levels during crew activities.

The crew quarters were designed to provide a personal, private area for a crewmember to rest, sleep, and work

and for personal activities. Work activities included reading/writing, computer usage, and review of reports and

procedures. Personal activities included changing clothes, reading/writing, and computer usage or watching movies or writing emails, listening to music, personal communication, and private work consultations. Crew quarters also provide limited stowage for personal items, clothing, and computer accessories. Currently there are a total of six crew quarters: two Russian crew quarters (Port and Starboard kayuta) located in the Russian segment in the Service Module and the other four crew quarters (CQs) are located in the US segment in Node 2. It has been estimated that long-duration crewmembers can expect to spend one-third of their entire mission inside one of the CQs. The ISS crew quarters sleep stations provided a quiet area for recovery (reduced acoustic stimulus to the ears) from daytime noise exposure levels. This recovery period was very similar to the recovery period promoted by the Occupational Safety and Health Administration (OSHA) for occupational noise exposure without hearing protection. A significant difference was that OSHA’s standard is based on workers who were exposed to high levels of noise during the 8-hour workday followed by 16 hours of auditory recovery for a 40-hour workweek followed by two days of auditory rest on the weekend. In the case of the ISS crewmembers, they were exposed constantly to the daytime noise exposure levels, whenever they are not inside their crew quarters, for the duration of their ISS mission (lasting approximately 6 months).

Noise levels in the Russian crew quarters (kayutas) have previously been a concern, but have decreased on the

average by approximately 10 dBA since levels first measured in November 2001 (see Fig. 4). Noise levels have been measured above 70 dBA (LEQ8) during Increment 6 and as low as 50 dBA (LEQ8) during Increment 25. When compared to the previously reported levels (increments 1-26), the sleep-time period noise levels (LEQ8) during the ISS increments 27-35 have continued to decrease in the kayutas by as much as 2 dBA (see Fig. 4a).

Figure 3a. Comparison of the distribution of LEQ16 during work hours in the US segment (5-dB ER). SOURCE: Acoustic dosimeter data collected on-orbit from November 2001 through April 2013.

Figure 3b. Comparison of the distribution of LEQ16 during work hours in the RS segment (5-dB ER). SOURCE: Acoustic dosimeter data collected on-orbit from November 2001 through April 2013.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

7

The ISS crew’s sleep-time noise exposure levels for crew quarters located in the US segment are shown in Fig. 5. During early stages of ISS, when the US crew quarters were not available, crewmembers slept in the Temporary Early Sleep Station (TeSS) located in the US Lab, and in locations within the other pressurized modules such as Node 1, Japanese Experiment Module (JEM), the Columbus module and even in a visiting vehicle. These locations were all considered temporary. The four permanent US crew quarters (Port, Starboard, Deck and Overhead) became available to ISS crewmembers starting in Increment 18. Overall, sleep-time noise levels in the permanent US crew quarters (CQs) have remained below the hearing loss risk level (62 dBA) (LEQ8). The measurements in the US CQs have been measured as low as 44 dBA (LEQ8) (increment 27) to as high as 59 dBA (LEQ8) (increment 31). When compared to the previously reported levels (increments 1-26), the sleep-time period noise levels (LEQ8) during the ISS increments 27-35 have remained statistically the same (with only a decrease of <1 dBA) (see Fig. 5a). The US and Russian crew quarters are adequately quiet, when doors are closed, to provide auditory rest and do not increase the risk for hearing loss. The exceedances of the sleep requirements (US: 49 dBA (LEQ8) and Russian: 50 dBA (LEQ8)) are considered, however, potentially disruptive to restful sleep. According to the World Health Organization (WHO) recommends a night noise exposure (Lnight) value of 40 dBA or lower to be the target of the night noise guideline to protect the public.13 However, WHO also recommends an Lnight value of 55 dBA or lower as an interim target when the 40 dBA level cannot be initially met. Crew debriefs have indicated that crew sleep had not been affected by ISS sleep station noise levels. Different types and sizes of HPDs are always available to crewmembers on ISS, if needed.

Figure 4. Sleep Dosimetry vs. ISS Increments (Russian Segment) – using 5-dB ER. SOURCE: ISS Acoustic Dosimetry Report (April – June 2013), Increments 35/36

Figure 4a. Comparison of the distribution of LEQ8 during sleep time hours in the RS segment kayutas (5-dB ER). SOURCE: Acoustic dosimeter data collected on-orbit from November 2001 through April 2013.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

8

Figure 5a. Comparison of the distribution of LEQ8 during sleep time hours in the US segment CQs (5-dB ER). SOURCE: Acoustic dosimeter data collected on-orbit from November 2001 through April 2013.

Figure 6 shows the distribution of LEQ levels during sleep hours. The data show that the noise levels in the kayutas, in the Russian segment, were higher than the crew quarter levels in the US segment. This followed the same trend from Fig. 3, where crewmembers working in the Russian segment were exposed to higher LEQ24 noise levels than crewmembers working in the US segment.

The distribution of LEQ levels for work (LEQ16),

sleep-time (LEQ16), and full-day (LEQ24) levels are shown in Fig. 7. The data show that ISS crewmembers were exposed to higher noise levels during the work period (LEQ16), as compared to the sleep-time period (LEQ8). The work period noise exposure level had a median level of 70 dBA (LEQ16), ranging from 63 to 82 dBA. The sleep-time period noise exposure levels had a median level of 55 dBA (LEQ8), ranging from 44 to 70 dBA. This resulted in a 15 dBA difference between the crew quarter sleep stations and the modules’ median levels. This difference could be due to crew quarter’s design features and also whether or not the crew quarter’s door was kept opened or closed during this sleep-time period, i.e., crew preferences. Overall, the crew quarter sleep stations provided a quiet area for recovery (reduced acoustic stimulus to the ears) from daytime noise exposure levels.

After reviewing the trend of the average noise exposure level data (combining US and Russian crewmember’s data), it was concluded that the noise exposure levels for the full-day (LEQ24) were very dependent on the noise levels from the work period (LEQ16) (see Fig. 8). The noise exposure levels during the work hours (LEQ16) played a major role in determining the full-day noise exposure level (LEQ24), but not the sleep-time period levels (LEQ8). The work and full-day equivalent noise levels were fairly constant throughout all 35 ISS Increments, with the exception of increments 31 and 32. The average noise exposure levels for the work hours fluctuated from 69 to 76 dBA (LEQ16)

Figure 5. Sleep Dosimetry vs. ISS Increments (US Segment) – using 5-dB ER. SOURCE: ISS Acoustic Dosimetry Report (April – June 2013), Increments 35/36

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

9

while the average noise levels for the full-day ranged from 66 to 73 dBA (LEQ24). The average noise exposure levels for the sleep-time period continue to decrease. The average levels continue to show a downward trend throughout the increments ranging from 53 dBA (increment 27) to 59 dBA (increment 29) (LEQ8), this data includes all six sleep stations.

B. Static location measurement After completing the 24-hour

crew-worn measurements for all six crewmembers, the dosimeters were then deployed on day three for a 24-hour session at three fixed locations. The acoustic dosimeters were cycled through each of the ISS pressurized modules or areas of concern, such as areas near exercise equipment, fans, etc. Measurements have been recorded in the US and Russian segments. The data logging feature on the dosimeters were a great tool for assessing and evaluating continuous or intermittent sources of noise in the environment. As an example, an acoustic dosimeter was deployed in Node 1 to assess the performance of an inter-module ventilation (IMV) fan (see Fig. 9). Figure 10 show the trend of the acoustic levels in Node 1. The continuous noise was shown to increase slightly by 5 dBA between March 2012 and February 2013. The noise levels in Node 1 returned to normal after the IMV fan flow straightener was cleaned in March 2013. The IMV fans are part of the ISS Environmental Control and Life Support System (ECLSS) for driving air circulation between the pressurized modules. The IMV fan flow straightener and other parts get clogged with debris from ISS and stalled the fan which significantly increased the noise levels. The increase and decrease in noise levels caused by the IMV fan was evident in the changes to the continuous noise levels between 10:30pm and 6:00am shown in Fig. 10.

III. Discussion This paper describes the ISS noise exposure monitoring program as well as an assessment of acoustic dosimeter

data collected since April 2011 to date. Acoustic data has been collected onboard ISS since it was first inhabited by three crewmembers on November 2001 (Increment 1). The data also provide trending information with regard to the work and sleep environments experienced by the crewmembers on ISS. The average noise level in the ISS work environment has tended to remain fairly constant, though has fluctuated from 69 to 76 dBA (LEQ16) during the timeframe from April 2011 to April 2013. In contrast, the sleep environment average noise level has declined, decreasing by approximately 2 dBA in the noise exposure levels in the kayutas located in the Russian Service Module, but in the US CQs, the levels have remained stable during this timeframe. However, the average noise level

Figure 6. Distribution of LEQ8 during sleep hours by location (5-dB ER). SOURCE: Acoustic dosimeter data collected on-orbit from November 2001 through April 2013.

Figure 7. Distribution of LEQ by time of day using 5-dB ER. SOURCE: Acoustic dosimeter data collected on-orbit from April 2011 through April 2013.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

10

for the full-day (LEQ24) is most closely tied to the work noise levels (LEQ16) and the variations seen in the work environment data log. Overall, there has been an improvement in the acoustical environment on ISS, with the exception of an environmental condition caused by off-nominal hardware condition (e..g.. clogged IMV fans). After maintenance was performed on the equipment (e.g. cleaning clogged fans), levels return to nominal levels. The measurements collected to date were highly dependent on the activities/tasks the crew on ISS, whether occupational

or leisure, engaged during their stay on ISS, as well as environmental conditions caused by clogged fans on ISS.

The sleep-time period noise exposure levels can vary

depending on many factors such as the crew quarter’s location (in US or Russian Segments), if the crew quarter’s door is opened or closed, and the CQ fan’s speed set to (low, medium or high), or if the crewmember used speakers to listen to music or watch movies. Many of these factors can contribute to the variations seen in the measured data. A better understanding of these factors will provide a better understanding of the contribution that each factor can add to the overall noise exposure level.

The static dosimetry data has proven to be an excellent

asset for evaluating hardware or payload performance (for example, evaluating clogged IMV fans), and can also assist as a preventive maintenance guide by providing correlation as to when maintenance should be performed.

The data suggests an improvement in the ISS acoustic

environment; although hearing loss has been documented in long-duration spaceflights, to date, clinically significant permanent threshold shift (PTS) have not been documented for ISS crewmembers.14,15,16,17,18 However, cases of temporary threshold shift (TTS) with subsequent recovery has occurred and have been documented. Lessons learned from past space programs have shown to be very beneficial to the ISS Program.

Figure 8. Crew-worn Acoustic Dosimetry (Average LEQ per ISS Increment) – using 5-dB ER. SOURCE: Acoustic dosimeter data collected on-orbit from April 2011 through April 2013.

Figure 9. Acoustic dosimeter in a static location in the Node 1 module on ISS. SOURCE: NASA Imagery

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

11

IV. Future Directions The crewmembers on ISS have several modules in which they can spend time during the day. Accurately

tracking their activities, tasks, and noise exposure in these modules is a significant task. The current acoustic dosimeters used onboard ISS have the capability for measuring and logging data in one-minute intervals. However, correlating crew activities to the measured data can be a difficult task unless a crewmember’s timeline is well defined with time stamps corresponding to completed activities. Currently, a well-defined correlation between the measured data and crew timeline is lacking. However an activity is currently being performed for collecting on-orbit data during the monthly measurement sessions, which will provide a basis for identification and mapping high-noise areas and activities on ISS that contribute significantly to the noise exposure experienced by the crew. This data is being compiled into the Noise Exposure Estimation Tool (NEET) where noise exposure is calculated and the need for HPDs is determined and documented in the Noise Hazard Inventory (NHI). The NEET and NHI has been developed by the JSC Acoustics Office. This NHI will be primarily based on the data collected with the acoustic dosimeter, using the 3-dB equal energy exchange rule. See Fig. 11 for a description of elements used in utilization of the NHI. However, there are some areas and activities onboard ISS where acoustic dosimeter data is lacking. For these cases, ground data and/or sound level meter (SLM) data collected on ISS will be used instead until the acoustic dosimeter data become available. When using SLM data, an additional 3 dBA will be added to the sound level meter measurement in order to account for the levels beyond the background levels (difference between acoustic dosimeter and SLM data).19,20,21 Studies have shown that when accessing noise levels that widely fluctuates (e.g., highly mobile workers – ISS crewmembers), SLM measurements tends to underestimate noise exposure levels by an average of 3 dBA.

Presently, hearing protection requirements are based on 24-hour noise exposure measurements which provide

little information as to the cause of the exposure (current Noise Level Constraint ISS Flight Rule). As a result, hearing protection usage is specified in hours per day with no consideration for when (according to acoustic loading) the HPD would be most effective. More specifically, this flight rule could be met by wearing HPDs after the highest noise exposure (e.g., during a more quiet part of the day), which offers no practical protection from the risk of hearing loss. As a result, the current flight rule is not implementable and is not enforced. While recommendations are made through the Flight Surgeons, Audiologist, and medical teams, JSC Noise Level Constraint Flight Rule B13-152 has been inconsistently employed and enforced.

The new, revised Noise Level Constraint ISS Flight Rule will be based on a 16-hour working time period (LEQ16)

and an 8-hour sleep-time period (LEQ8), as measured by the acoustic dosimeter or by the data compiled in the NEET.

Figure 10. Node 1 (Acoustic Dosimeter Static Measurement). SOURCE: ISS Acoustic Dosimetry Report (April – June 2013), Increments 35/36

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

12

If the crewmember is exposed to an LEQ16 greater than 72 dBA, they will be directed to wear appropriate HPDs when performing tasks and activities and when high noise exposure levels are present. These activities and noise exposure levels will be identified in the ISS increment-specific NHI. If the work-day LEQ16 is greater than 60 dBA, then the Flight Surgeon will recommend to the affected crewmember that appropriate HPDs be used, based on the individual needs of the crewmember and the levels and durations of the noise exposure. This information will also be identified in the ISS increment-specific NHI. This revised flight rule sets forth noise constraints according to type of activity and duration (16 hours of crew work period, and 8 hours of sleep-time period), and is based on noise exposure levels measured and calculated (from sound levels and corresponding exposure durations) using a 3-dB equal energy exchange rate. These exposure levels are based on WHO guidelines that state that for ground conditions, “hearing loss is not expected to occur at LEQ8 levels of 75 dBA or lower, even for prolonged occupational noise exposures.”22 This level corresponds to an LEQ16 of 72 dBA or lower using the internationally-accepted 3-dB equal energy exchange rate. In addition, the WHO states, “It is expected that environmental and leisure-time noise with an LEQ24 of 70 dBA or lower will not cause hearing impairment in the large majority of people, even after a lifetime exposure.” This LEQ24 level of 70 dBA corresponds to a LEQ16 “work” level of 72 dBA with a LEQ8 “sleep” level of 62 dBA (hearing risk level) or lower using the 3-dB exchange rate.

If the 8-hour sleep-time period noise exposure level (LEQ8), as measured by the ISS acoustic dosimeter, exceeds

50 dBA (sleep disturbance level), the flight surgeon will inform the affected crewmember of steps to mitigate the noise. According to the WHO guidelines, an LEQ8 level of 55 dBA or higher “is considered extremely dangerous for public health.”21 The most frequently occurring adverse health effects in a sizeable proportion of the population are high irritation and sleep disturbances. There is evidence that the risk of cardiovascular disease increases.” If measured night-time noise exposure levels exceed 50 dBA, this revised flight rule will prompt discussions between

Figure 11. Block Diagram of Elements Used in Implementation of New Flight Rule for ISS Noise Level

Constraints, B13-152 (Operational Concept).

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

13

the flight surgeon and crewmember, over private communication path, regarding fitfulness of sleep and how to reduce possible disruption of sleep by night-time noise. The sleep-time period noise exposure levels can vary depending on many factors, as previously mentioned, such as where the crew quarter is located, if the crew quarter’s door is opened or closed, and the speed setting of the crew quarter’s fan. Recommended actions may include: closing the crew quarter’s door and reducing the sound level of noise producing hardware. Use of HPDs can also be an effective action to reduce sleep disturbances.

The NHI will provide a correlation between noise exposure increments and identified activities and locations so that informed recommendations for when the crew should wear hearing protection can be made prior to noise exposure. The NHI will be updated as often as acoustic dosimeter or SLM data are provided or if any environmental condition changes or equipment changes (e.g. clogged IMV fan) becomes available and the NEET is updated. In addition, the data in the NEET will be analyzed to determine sources of excessive noise and indicate need for future noise mitigations. The information, gathered through implementation of a data logging activity, will be correlated on the ground with the time-dependent sound levels measured by the current acoustic dosimeters, and the NHI will be developed for the specific ISS increment (see Fig. 11). In this figure, we can see how the data collected is used by the NEET to estimate the noise exposure for crewmembers working in the Russian and the US segments, which then generates an NHI for ground controllers (flight crew surgeons and biomedical engineers) and an NHI for advising the crew re: which upcoming activities/tasks warrant HPD use. The NHI will reduce the risk for noise-induced hearing loss, and will improve voice communications by avoiding non-productive mandated hearing protection use. The NEET and NHI will be used for implementing the revised Noise Level Constraint ISS Flight Rule that is based on a “task-based” hearing conservation approach. Task-based methods have distinct advantages over full-shift methods in that they provide a better understanding of sources of high noise exposure.23,24 The acoustic dosimeter and SLM data will be used to estimate the crew noise exposure. The NEET will also allow personnel in Houston’s NASA Mission Control Center make predictions and recommendations to Flight Surgeons and crewmembers. The NEET will use ground data and noise level data from the acoustic dosimeter and SLM on-orbit surveys of 60+ specific locations and environmental conditions onboard ISS. Figure 12 shows an example of a screen shot of the NEET. Here, five activities from the 60+ locations and activities in our database have been selected from the drop-down menu as planned for an upcoming day for a crewmember that will spend the majority of its workday in the US segment. Using the information (tasks) and duration from the crewmember’s planned schedule along in the NEET we can then determine that the HPDs are not required, but recommended (LEQ16 > 60 dBA). In another example we can see a scenario where the NEET will determine that the crewmember will require the use HPDs for certain tasks or activities (see Fig. 13). This particular crewmember that will spend the majority of its time in the Russian segment, performing these four activities will require the use of HPDs when using a treadmill (e.g. T2) and will be recommended to use HPDs during the other three known activities/locations on ISS.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

14

V. Conclusions Crew-worn acoustic dosimetry data have been collected onboard ISS since November 2001, when the ISS was

initially occupied by the first three crewmembers. During ISS increments 27-35 (April 2011 – April 2013), data have shown that acoustic requirements at all levels and noise control mitigations have produced a decrease (by approximately 2 dBA) in sleep-time noise exposure levels in the Russian kayutas. In the US CQs, levels have remained the same during this period. The work period noise levels have increased slightly in the US segment and in the Russian segment levels have remained constant during this time period. This slight increase, as previously mentioned, was due to changes in the environment produced by off-nominal equipment conditions. Though the levels returned to nominal after modifications were made to the affected equipment (e..g. cleaning clogged IMV fans). Static dosimetry has helped identify these hardware anomalies. As we learn how to better correlate the crew timeline with the measured acoustic dosimetry data and populate the NHI, our ability to protect the crewmembers onboard ISS will be enhanced. As we move to the revised flight rule, the implementation of the NHI and predicting the crew noise exposure levels with the NEET will be vital for maintaining the health and safety of all crewmembers onboard ISS.

Acknowledgments The authors would like to thank the ISS Biomedical Engineers for helping with the crew procedures, training,

anomaly resolutions and serving as the liaison to the ISS crew; the hardware engineers for keeping the acoustic dosimeters certified and ready for flight; and the International Partners for their collaboration with the noise exposure monitoring program.

Figure 12. Noise Exposure Estimation Tool Screen-Shot (Example 1).

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

15

References 1Limardo, J. G., and Allen, C. S., “Analysis of Noise Exposure Measurements Acquired Onboard the International Space

Station,” Proceedings of International Conference on Environmental Systems 2011. American Institute of Aeronautics and Astronautics, AIAA 2011-5137, 2011.

2SSP 50260, “International Space Station Medical Operations Requirements Document (MORD),” February 2006. 3JSC 28913, “Medical Requirements Integration Document (MRID),” Rev A, March 2005. 4SSP 50260-1, “ISS Generic Groundrules, Requirements and Constraints (GGR&C), Part 1: Strategic and Tactical Planning,”

Rev E, January 2011. 5SSP 50260-2, “ISS Generic Groundrules, Requirements and Constraints (GGR&C), Part 2: Execute Planning,” Rev C,

February 2011. 6SSP 54025_54026-ANX 4, “Increment Definition and Requirements Document (IDRD) for Increments 25 and 26, Annex 4:

Medical Operations and Environmental Monitoring,” May 2010. 7NSTS-1282, “ISS Generic Operational Flight Rules,” Vol. B, B13-152, “Noise Level Constraints.” 8Goodman, J. R., “International Space Station Acoustics,” NOISE-CON 2003 Conference, Cleveland, OH, 2003. 9OSHA Standard, “Occupational Noise Exposure,” 29 CFR 1910.95.

10NIOSH, “Preventing Occupational Hearing Loss – A Practical Guide,” No. 96-110, June 1996. 11Department of Defense Instruction, “DoD Hearing Conservation Program,” No. 6055.12, March 5, 2004. 12Allen, C. S., and Denham, S. A., “International Space Station Acoustics – A Status Report,” Proceedings of International

Conference on Environmental Systems 2011. American Institute of Aeronautics and Astronautics, AIAA 2011-5128, 2011. 13Kim, R., and van den Berg, M., “Summary of night noise guidelines for Europe,” Noise and Health, 12:47, 2010, pp. 61-63. 14Buckey, J. C., Musiek, F. E., Klein-Schoder, R., Clark, J., Hart, S., and Havelka, J., “Hearing Loss in Space,” Aviation,

Space, and Environmental Medicine, Vol. 72, No. 12, December 2001, pp. 1121-1124. 15Clark, J. B., and Allen, C. S., “Acoustic Issues,” Principles of Clinical Medicine for Space Flight, 1st ed., Springer, 2008,

Chap. 24. 16Hodge, D. C., and Garinther, G. R., “Noise and Blast,” Bioastronautics Data Book, 2nd ed., NASA SP-3006, 1973, Chap.

15.

Figure 13. Noise Exposure Estimation Tool Screen-Shot (Example 2).

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

American Institute of Aeronautics and Astronautics

16

17Roller, C. A., and Clark, J. B., “Short-duration space flight and hearing loss,” Otolaryngology – Head and Neck Surgery, July 2003, pp. 98-106.

18Koros, A. S., Adam, S. C., Wheelwright, C. D., “Noise Levels and their Effects on Shuttle Crewmembers’ Performance: Operational Concerns,” N94-11538, 1994.

19Hansen, D. J., Adams, W G., and Hochberg, R. A., “Comparison of Sampling Strategies Used During a Machine Shop Noise Survey,” Appl. Ind. Hyg., Vol. 4, No. 3, March 1989, pp. 75-80.

20Shackleton, S., and Piney, M. D., “A Comparison of Two Methods of Measuring Personal Noise Exposure,” Ann. Occup. Hyg., Vol. 28, No. 3, 1984, pp. 373-390.

21Jones, C. O., and Howie, R. M., “Investigations of Personal Noise Dosimeter for use in Coalmines,” Ann. Occup. Hyg., Vol. 25, No. 3, 1982, pp. 261-277.

22Berglund, B; Lindvall T, and Schwela D, “Guidelines for Community Noise”, World Health Organization, (Geneva,1999). 23Seixas, N. S., Ren, K., Neitzel, R., Camp, J., and Yost, M., “Noise Exposure among Construction Electricians,” AIHAJ,

Vol. 62, 2001, pp. 615-621. 24Seixas, N. S., Sheppard, L., and Neitzel, R., “Comparison of Task-Based Estimates with Full-Shift Measurements of Noise

Exposure,” AIHA Journal, Vol. 64, 2003, pp. 823-829.

Dow

nloa

ded

by J

osé

Lim

ardo

on

July

15,

201

3 | h

ttp://

arc.

aiaa

.org

| D

OI:

10.

2514

/6.2

013-

3516

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.