Sound-Exposure Levels Experienced by Music Students and Correlation to Hearing Loss

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1 Sound-Exposure Levels Experienced by Music Students and Correlation to Hearing Loss Item Type text; Electronic Dissertation Authors Smith, Jason D. Publisher The University of Arizona. Rights Copyright is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 04/07/ :43:45 Link to Item

2 SOUND-EXPOSURE LEVELS EXPERIENCED BY MUSIC STUDENTS AND CORRELATION TO HEARING LOSS by Jason Smith Copyright Jason Smith 2017 A Dissertation Submitted to the Faculty of the DEPARTMENT OF SPEECH, LANGUAGE, AND HEARING SCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF AUDIOLOGY In the Graduate College THE UNIVERSITY OF ARIZONA 2017

3 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Jason Smith, titled Sound-Exposure Levels Experienced by Music Students and Correlation to Hearing Loss and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Audiology. Date: 4/13/2017 David Velenovsky, PhD, CCC-A Date: 4/13/2017 James Dean, AuD, CCC-A Date: 4/13/2017 Brad Story, PhD Date: 4/13/2017 Burris Duncan, MD Final approval and acceptance of this dissertation is contingent upon the candidate s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. Date: 4/13/2017 Dissertation Director: David Velenovsky, PhD, CCC-A 2

4 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of the requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that an accurate acknowledgement of the source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: Jason Smith 3

5 Acknowledgements Thanks to the University of Arizona Fox School of Music staff and faculty, including Deon Dourlein, Senior Technical Director; Edward Reid, School Director; Dr. Rex Woods, Former Director; and Dr. Paula Fan, Professor of Music. Also thanks to members of the Department of Speech, Language, and Hearing Sciences, including Dr. David Velenovsky, Dr. James Dean, and Dr. Brad Story, and collaborating undergraduate students Holly Durr and Sarah MacKenzie. Statistical Analysis was provided by Dr. Mark Borgstrom in the Research Computing group of University Information Technology Services (UITS). Thanks to David Ahlstrom and colleagues at Larson Davis for the generous donation of Spark 703+ dosimetry equipment. This research would not be possible without their kind contribution. 4

6 Table of Contents Abstract Introduction Method Sound Exposure Results Distortion Product Otoacoustic Emissions Results Discussion References List of Figures Figure 1 Leq after two hour practice session Figure 2 TWA after two hour practice session Figure 3 Plot of Leq Figure 4 Plot of peak sound levels Figure 5 DPOAE difference for left ear Figure 6 DPOAE difference for right ear Figure 7 Long-term average spectra

7 Abstract It is known that musicians are exposed to potentially harmful sound levels during the course of regular practice, rehearsal, and performance. As a result, these individuals may have an increased risk of noise-induced hearing loss (NIHL). Previous research has shown that in typical daily practice, musicians can exceed daily recommended exposure limits (O Brien et al., 2013). This research suggests that classical musicians are at high risk for NIHL according to the National Institute for Occupational Safety and Health (US Department of Health and Human Services, 1998) and the Occupational Safety and Health Administration (OSHA) guidelines. In addition, distortion-product otoacoustic emission (DPOAE) amplitude shifts have been found to be a sensitive measure for impact of high noise levels on inner-ear function (Lonsbury-Martin et al., 1990). The very livelihoods of musicians could depend on the development of NIHL awareness and prevention strategies. This study reports the sound-level exposures that University of Arizona music students experience in two hours of solitary practice and whether any correlative change in DPOAE amplitude occurred. Utilizing noise dosimetry, measurements of average sound levels and equivalent exposure for an eight-hour period were taken and compared to NIOSH and OSHA guidelines. Changes in inner-ear function were measured by DPOAE amplitudes taken immediately before and after each practice session. The goal of this research is to present data regarding sound-level exposure and address any significance in the correlative relationship between practice-session exposure levels and any shift in outer hair-cell function as determined by pre- and post-practice DPOAE evaluation. Introduction Hearing loss resulting from exposure to noise is a risk that is common in occupations involving high sound levels such as construction, farming, military, law enforcement, and air-traffic ground crews (OSHA Safety and Health Topics: Occupational Noise Exposure, n.d.). Excessive noise exposure can damage the outer hair cells of the cochlea and subsequently impact hearing thresholds a temporary shift that will become permanent after repeated similar exposures. This permanent threshold shift is called noise induced hearing loss (NIHL) and is irreversible (US Department of Health and Human Services, 1998). The National Institute for Occupational Safety and Health (NIOSH) has outlined guidelines for safe daily noise-exposure levels. These guidelines provide the foundation for Occupation Safety and Health (OSHA) regulations that must be followed for employees in jobs with frequent noise exposure to avoid hearing impairment. NIOSH recommends that noise exposure not exceed an average level of 85 dba over the course of eight hours. OSHA regulations, based on NIOSH recommendations, require noise exposure levels of 90 dba or less for an eight hour period (OSHA Noise and Hearing Conservation Technical Manual Chapter: Appendix II:A. General Industry Standard, n.d.). 6

8 Musicians can also be subjected to high noise levels. This may seem obvious for musicians who use high levels of amplification and distortion when playing their instruments such as the electric guitar, but surprisingly, classical musicians may also be at risk. A typical classical musician spends up to six hours practicing, often in small rooms provided by music departments in high schools, colleges, and music academies. Phillips and Mace (2008) measured sound-level exposures for university students in practice and found that nearly half of the subjects were exposed to levels of sound in excess of 85 db the level at which OSHA requires the implementation of a hearing conservation program (OSHA Section IV, n.d.). A subsequent study also reported evidence to suggest that professional musicians can exceed daily allotments of noise exposure within two hours of practice (O Brien et al., 2013). As a result, these individuals have an increased risk of noise-induced hearing loss (NIHL). Standards for sound-level measurements have been established by NIOSH and include the use of a noise dosimeter to obtain personal exposure data over predetermined periods of time (OSHA Occupational Noise Industry Standards, n.d.). The dosimeter allows researchers to log real-time sound-level information while also calculating the average level for the entire exposure duration. These dosimeter calculations make it possible to compare data to NIOSH recommended exposure levels. Determining any correlation between sound-exposure levels and hearing loss requires a sensitive measure of hearing a baseline evaluation of hearing function prior to the practice session as well as a post-session evaluation. Distortion-product otoacoustic emission (DPOAE) measurements are used clinically as an effective indicator of inner-ear function and complement the audiologic evaluation (Lonsbury-Martin et al., 1990). Shifts in DPOAE amplitude have also been found to correlate well with changes in hearing thresholds (Job et al., 2009; Miller et al., 2006). The NIOSH recommended exposure limit (REL) for occupational noise exposure is 85 decibels, A-weighted, as an eight-hour time-weighted average. Exposures at or higher than this level are considered hazardous (US Department of Health and Human Services, 1998). The purpose of this research was to determine maximum sound-pressure levels as well as equivalent sound levels according to NIOSH guidelines during a single individual two-hour practice session for a variety of musical instruments. The specific aim was to identify the REL of musicians playing different instruments in practice and the recommended allowable exposures to sound according to NIOSH. 7

9 Method Eight University of Arizona music students were recruited and ranged in age from Musical instruments played were piano (two participants), trombone (two participants), trumpet, French horn, flute/piccolo, and snare drum. The measurement space was a typical practice room in the Fred Fox School of Music. The room was 14 x 12 x 9 6 (1,596 cubic feet). Approximately half of the wall surface (798 square feet) was covered in acoustic tile while two walls (120 square feet) consisted of painted concrete and the floor (133 square feet) was tile. Room reverberation was measured using a Larson Davis Model 831 Class 1 Sound Level Meter. Reverberation time, defined as the time it takes for the sound level to decay by 60 db following an impulse sound (RT60), was seconds (average of three measurements) at 1000 Hz (Chen & Brueck, 2012). Extended reverberation can produce persistent residual noise that is added to the ongoing incident sound potentially impacting the overall sound-exposure level (Beranek, 2006). The recommended RT60 for maximization of musical sound quality in music halls of similar volume ranges from 0.95 to 1.25 seconds depending on the genre of music being played (Hemond, 1983; Hall, 2002). This room had a considerably shorter RT60, resulting in less of a reverberation effect than created by typical music halls. The Level Equivalent (Leq) is defined as the equivalent continuous sound during a given time period, taking into account the variation in levels during that period (O Brien et al., 2013; OSHA Section III: Chapter 5: Noise, n.d.). Leq may also be thought of as the average level for the duration. The time weighted average (TWA) is defined as the expected sound level after eight hours that would result from the Leq of the sample period (OSHA Section III: Chapter 5: Noise, n.d.). The peak level (Lpeak) is defined as the maximum sound pressure level recorded over a period of time (OSHA Section III: Chapter 5: Noise, n.d.). Other dosimeter measurements include Ln (L10, L50, L90), which is defined as the sound level that has been exceeded n% of the time during a given time period. Measurements were obtained using the A-weighted scale for comparison to NIOSH guidelines. NIOSH, OSHA, and the American Conference of Governmental Industrial Hygienists (ACGIH) have adopted this scale as the standard for occupational noise measurements. This scale was developed based on equal loudness contours (Fletcher & Munson, 1933) and has since been used as the standard in sound-level meters for occupational noise-level measurements (OSHA Noise and Hearing Conservation Technical Manual Chapter: Appendix I:A-4, n.d.; Rawool, 2012). Participants were asked to engage in a typical two-hour practice session during which sound levels were monitored using a Larson Davis Spark 703+ Noise Dosimeter with the microphone 8

10 clipped to their right collar in most cases. For instruments that produced lateralized output, the microphone was clipped to the corresponding collar. Measurements were taken using an A- weighted scale in accordance with NIOSH and OSHA standards. The recorded data were then extracted using the Larson Davis Blaze software and compared to NIOSH guidelines. Immediately preceding and immediately following each practice session, DPOAE measurements for each ear were collected using a Mimosa HearID Auditory Diagnostic System. Based on previous research, DPOAE data would provide information regarding the outer hair cell function of each musician and detect any changes after the exposure period (Lonsbury- Martin et al., 1990; Müller et al., 2010). The exported data were then analyzed using mixedmodel statistical analysis. Ten minute digital recording samples were also taken for trombone, piano, flute, and piccolo in order to produce long term average spectra data from each instrument. These methods were approved by the University of Arizona Institutional Review Board. Results Sound Exposure Results Data were collected to represent the level of exposure during the two-hour practice session and extrapolated to represent each musician s likely exposure level for the entire day as a result of this exposure. Figure 1 shows the Leq for each instrument after two hours of practice: snare drum (96.6 dba), French horn (94 dba), flute/piccolo (93.3 dba), trombone 1 (92.9 dba), trumpet (86.4 dba), trombone 2 (91.7 dba), piano 1 (83.5 dba), and piano 2 (80.9 dba). Had the musicians continued to experience similar levels of exposure for the remaining six hours of their eight-hour day, their average exposure level would be similar to this measurement. That would result in excessive sound exposure base on NIOSH guidelines for all subjects except the two pianists. The data shown in Figure 2 represent the time weighted average (TWA) for each instrument. The TWA data allow for direct comparison to NIOSH occupational-sound recommended exposure limits (REL). This number represents the musician s likely exposure for the entire eight-hour day, provided the musician did not engage in any additional high-level sound exposure (greater than 80 dba) for the remaining six hours. Five of the eight instruments averaged at or above the NIOSH REL of 85 dba (US Department of Health and Human Services, 1998): snare drum (90.5 dba), French horn (87.9 dba), flute/piccolo (87.4 dba), trombone 1 (86.8 dba), and trombone 2 (85.6 dba). These musicians are at risk for noise-induced hearing loss per NIOSH guidelines. The trumpet (80.4 dba), piano 1 (77.5 dba), and piano 2 (74.8 dba) were all 9

11 recorded with a TWA of less than the NIOSH REL and are not at risk for noise-induced hearing loss provided they did not engage in any additional high-level sound exposure for the remainder of the day. Figure 1: Leq in dba for each instrument after two hours of practice. Figure 2: TWA for each instrument after two hours of practice. Figure 3: Plot of Leq for the snare drum, flute/piccolo, trumpet, and piano over a two-hour period. Figure 4: Plot of peak sound levels for the snare drum and flute/piccolo over a two-hour period. A plot of Leq for the snare drum, flute/piccolo, trumpet, and piano 2 over a two-hour practice period (average of 50 samples every second) is shown in Figure 3. This figure illustrates the variation of sound level over the two-hour period, including moments of relative quiet represented by dips down to dba. Notably, these instruments remain relatively consistent in their sound-level output throughout the session and are in agreement with the Leq calculated for the entire two-hour session. For example, the snare drum two-hour Leq was 90.5 dba and the Figure 3 plot of real-time Leq suggests that there were very few outliers in sound-level output impacting the two-hour Leq calculation. 10

12 The data shown in Figure 4 represent the plot of peak sound levels for the snare drum and flute/piccolo over a two-hour period (sampled every second). Note the snare drum peak level reaches 135 dba, only 5 db below the NIOSH recommended single or impulse exposure limit of 140 dba (OSHA General Industry Standard, n.d.). The apparent rise in peak levels in the second half of the two-hour session most likely relate to the nature of the musical piece this participant chose. This rise is not demonstrated in the Leq (average of 50 samples every second) shown in Figure 3 and therefore only represents maximum measured output (highest level of the 50 samples taken every second). Distortion Product Otoacoustic Emissions Results Mixed model statistical analysis was used to analyze the significance between pre- and postexposure DPOAE amplitudes. Any significant reduction in distortion-product amplitude would be suggestive of changes in outer hair cell function as a result of acoustic trauma (Lonsbury- Martin et al., 1990). Differences between pre- and posttest DPOAE amplitudes were not statistically significant in this study. Considerable variability among subjects was also observed, suggesting that individual susceptibility to sound exposure may also have an impact on postpractice DPOAE amplitude. In Figure 5, the differences between pre/post DPOAE amplitudes for each subject s left ear is shown for each DP frequency; Figure 6 shows the difference between pre/post DPOAE amplitudes of right ears for each subject at each DP frequency. A negative number indicates a decrease in DPOAE amplitude following two hours of practice. Figure 5: The left ear difference between pretest and posttest DPOAE results for all subjects. Figure 6: The right ear difference between pretest and posttest DPOAE results for all subjects. 11

13 Discussion The long-term average spectra (LTAS) for each instrument indicates that the greatest intensities occur below 3000 Hz. Additionally, the trombone, French horn, and piano demonstrate the greatest intensities below 1000 Hz. In Figure 7, the LTAS for five instruments are shown. These data have been normalized to maximum amplitude and colored lines representing DPOAE frequencies (f1 in red, f2 in blue) and expected distortion product (DP in green) frequencies are shown for reference. Figure 7: The longterm average spectra (LTAS) for five instruments (normalized to maximum amplitude). As shown in Figure 7, LTAS data measured for the trombone, French horn, and piano demonstrate the greatest intensities below 1000 Hz. At intensity levels below 80 db, the human ear is less sensitive to loudness at frequencies below 1000 Hz. At levels above 80 db, the human ear s perceives loudness more similarly across frequencies, whether below or above 1000 Hz. This is demonstrated in the equal-loudness contour developed by Fletcher & Munson (1933). Measurements were made using the industry standard A-weighting scale for comparison to NIOSH guidelines; however, there may be a case for use of the C-weighting measurements in future studies. The C-weighted scale is used for measurement of high-intensity sound (above 80 db) and has a broader frequency response at frequencies below 1000 Hz (Rawool, 2012). As such, it could be argued that use of C-weighting rather than A-weighting at higher levels (above 80 db) may be a more appropriate measure of sound levels, in regards to their relationship to human hearing sensitivity at higher levels and potential for causing noise-induced hearing loss. This study was limited to two hours of solitary practice and does not include any practice or ensemble rehearsal time beyond this two-hour session. The data gathered suggest that university music students are routinely at risk for elevated sound-exposure levels, based on 12

14 NIOSH guidelines for the prevention of noise-induced hearing loss. In addition, there is evidence to suggest that exposure to high-level impulse sounds such as those demonstrated by the snare drum can cause acoustic trauma. These exposures may lead to NIHL even if the NIOSH recommended impulse limit of 140 dba is not reached (Rezaee et al., 2012). Musicians reviewing these data should consider taking care to limit exposure by use of personal hearing protection during solitary practice. University Music Programs should also consider establishing hearing conservation programs whereby incoming students engage in initial audiologic evaluation, are fitted with musician-grade personal hearing protection, and engage in periodic audiologic evaluation throughout their academic career for signs of noise-induced hearing loss. As noted above, differences between pre- and posttest DPOAE amplitudes were not statistically significant in this study. This is possibly attributable to a small sample size, variability in DPOAE probe placement resulting in acoustic changes in the ear canal, and fluctuations in noise floor due to environmental changes and/or body noise from each subject. As such, additional research to determine hearing loss and sound-exposure correlation is needed. Additional steps for future study include multiple replicated pre/post DPOAE measurements for each subject and the addition of pre/post audiometric evaluations to complement DPOAE measures. Future research is also needed to determine the objective and subjective impact of hearingprotection devices (HPD) on the musician experience, including ear-canal measurements of HPD spectra as well as actual level of attenuation. In addition, more data regarding the uptake of HPDs among student and professional musicians is needed. 13

15 References 1. Beranek, L. L. (2006). Analysis of Sabine and Eyring equations and their application to concert hall audience and chair absorption. The Journal of the Acoustical Society of America, 120(3), Chen, L., & Brueck, S. E. (2012). Noise Evaluation of Elementary and High School Music Classes and Indoor Marching Band Rehearsals Alabama. 3. Fletcher, H., & Munson, W. A. (1933). Loudness, Its Definition, Measurement and Calculation*. Bell System Technical Journal, 12(4), Hall, D. E. (2002). Musical acoustics. Brooks Cole. 5. Hemond, C. J. (1983). Engineering acoustics and noise control. Prentice Hall. 6. Job, A., Raynal, M., Kossowski, M., Studler, M., Ghernaouti, C., Baffioni-Venturi, A.,... & Guelorget, A. (2009). Otoacoustic detection of risk of early hearing loss in ears with normal audiograms: a 3-year follow-up study.hearing research, 251(1), Lonsbury-Martin, B. L., & Martin, G. K. (1990). The clinical utility of distortion-product otoacoustic emissions. Ear and hearing, 11(2), Miller, J. A. L., Marshall, L., Heller, L. M., & Hughes, L. M. (2006). Low-level otoacoustic emissions may predict susceptibility to noise-induced hearing loss. The Journal of the Acoustical Society of America, 120(1), Müller, J., Dietrich, S., & Janssen, T. (2010). Impact of three hours of discotheque music on pure-tone thresholds and distortion product otoacoustic emissions. The Journal of the Acoustical Society of America,128(4), O'Brien, I., Driscoll, T., & Ackermann, B. (2013). Sound exposure of professional orchestral musicians during solitary practice. The Journal of the Acoustical Society of America, 134(4), OSHA. (n.d.). Noise and Hearing Conservation Technical Manual Chapter: Appendix I:A-4. A- Weighted Network. Retrieved from OSHA. (n.d.). Noise and Hearing Conservation Technical Manual Chapter: Appendix II:A. General Industry Standard. Retrieved from OSHA. (n.d.). Safety and Health Topics: Occupational Noise Exposure. Retrieved from OSHA. (n.d.). Section III:Chapter 5. Noise. Retrieved from OSHA. (n.d.). Section IV: What constitutes an effective hearing conservation program? Retrieved from Phillips, S. L., & Mace, S. (2008). Sound level measurements in music practice rooms. Music Performance Research, 2(1), Rawool, V. W. (2012). Hearing Conservation: In Occupational, Recreational, Educational, and Home Settings. New York, NY: Thieme. 14

16 18. Rezaee, M., Mojtahed, M., Ghasemi, M., & Saedi, B. (2012). Assessment of impulse noise level and acoustic trauma in military personnel. Trauma monthly, 16(4), US Department of Health and Human Services. (1998). Criteria for a Recommended Standard: Occupational Noise Exposure Revised Criteria.Cincinnati, OH,