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|Year : 2013
: 15 | Issue : 65 | Page
|Auditory risk assessment of college music students in jazz band-based instructional activity
Kamakshi V Gopal1, Kris Chesky2, Elizabeth A Beschoner1, Paul D Nelson1, Bradley J Stewart1
1 Department of Speech and Hearing Sciences, College of Music, University of North Texas, Denton, Texas, USA
2 UNT College of Music Texas Center of Music and Medicine, College of Music, University of North Texas, Denton, Texas, USA
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|Date of Web Publication||15-Jun-2013|
It is well-known that musicians are at risk for music-induced hearing loss, however, systematic evaluation of music exposure and its effects on the auditory system are still difficult to assess. The purpose of the study was to determine if college students in jazz band-based instructional activity are exposed to loud classroom noise and consequently exhibit acute but significant changes in basic auditory measures compared to non-music students in regular classroom sessions. For this we (1) measured and compared personal exposure levels of college students (n = 14) participating in a routine 50 min jazz ensemble-based instructional activity (experimental) to personal exposure levels of non-music students (n = 11) participating in a 50-min regular classroom activity (control), and (2) measured and compared pre- to post-auditory changes associated with these two types of classroom exposures. Results showed that the L eq (equivalent continuous noise level) generated during the 50 min jazz ensemble-based instructional activity ranged from 95 dBA to 105.8 dBA with a mean of 99.5 ± 2.5 dBA. In the regular classroom, the L eq ranged from 46.4 dBA to 67.4 dBA with a mean of 49.9 ± 10.6 dBA. Additionally, significant differences were observed in pre to post-auditory measures between the two groups. The experimental group showed a significant temporary threshold shift bilaterally at 4000 Hz (P < 0.05), and a significant decrease in the amplitude of transient-evoked otoacoustic emission response in both ears (P < 0.05) after exposure to the jazz ensemble-based instructional activity. No significant changes were found in the control group between pre- and post-exposure measures. This study quantified the noise exposure in jazz band-based practice sessions and its effects on basic auditory measures. Temporary, yet significant, auditory changes seen in music students place them at risk for hearing loss compared to their non-music cohorts.
Keywords: Dosimeter, jazz ensemble, music-induced hearing loss, pure tone thresholds, transient-evoked otoacoustic emissions
|How to cite this article:|
Gopal KV, Chesky K, Beschoner EA, Nelson PD, Stewart BJ. Auditory risk assessment of college music students in jazz band-based instructional activity. Noise Health 2013;15:246-52
|How to cite this URL:|
Gopal KV, Chesky K, Beschoner EA, Nelson PD, Stewart BJ. Auditory risk assessment of college music students in jazz band-based instructional activity. Noise Health [serial online] 2013 [cited 2014 Dec 20];15:246-52. Available from: http://www.noiseandhealth.org/text.asp?2013/15/65/246/113520
| Introduction|| |
Noise-induced hearing loss (NIHL) is one of the most prevalent occupational diseases in the world as millions of people around the globe are exposed to high levels of noise at their work place. It is estimated that 10% of adults in industrialized countries have NIHL.  NIHL has been researched quite extensively; however, most of that literature circumvents the area of music-induced hearing loss (MIHL). The term MIHL was coined to denote acquired hearing loss due to loud music exposure.  All types of auditory signals, including music, with significant intensity and duration are known to increase the risk of hearing loss. , The number of young adults and adolescents that are exposed to loud music has increased in the recent past, as more people play and listen to loud music without recognizing the risk for permanent hearing loss. There is, however, a growing concern regarding hearing impairment from music exposure, especially in musicians, music students, and professionals in the music industry, as they represent an occupational group that is very dependent on the optimal functioning of the auditory system. ,,
A review of the literature indicates that investigations of MIHL have focused on professional musicians, people working in music venues, and general public listening to loud music for long durations. Several studies have shown that classical musicians are exposed to 83-112 dBA levels during practice and rehearsal session. ,,, The maximal sound peaks in music sessions, orchestral settings, rock/pop concerts, music bars and discotheques are reported to exceed 100 dBA levels. ,,, Sound levels have been measured in routine instructions activities offered in public school and tertiary programs. For example, sound levels were measured in routine ensemble-based instructional activities (wind band) in over a 15 week period and the average dose level for 42 individual events was 109.5% and ranged from 53.8% to 166.9%. 
With exposure to such high levels of noise, it is quite common to see hearing loss in musicians and non-professional musicians. , It has been reported that hearing loss in musicians is as high as 50% , with even higher percentage of people reporting hearing loss-related symptoms such as tinnitus, hyperacusis and distortion.  Students exposed to high levels of music were found to have moderate temporary threshold shifts (TTSs) which correlated with their history of personal exposure, most significantly at 4 kHz. Furthermore, Transient-evoked otoacoustic emission (TEOAE) responses in these young college adults showed overall weaker responses compared to students with less exposure to music.  Pure tone thresholds in 16 nonprofessional rock musicians measured before and after a 90-min rehearsal session were found to be significantly different, with poorer thresholds for frequencies from 0.5 kHz to 8 kHz obtained after the rehearsal session.  Review articles on music exposure and its risk to hearing loss have been published earlier. ,
Because sound levels generated during instructional activities are capable of reaching exposure levels sufficient to harm hearing, prevention of MIHL has become a major concern of the Performing Arts Medicine Association,  the Centers for Disease Control  and the National Association for Music Education. , Similar concerns exist for music schools and conservatories in the European Union. , In response, the National Association of Schools of Music (NASM) recently ratified a new accreditation standard that now requires accredited schools of music in the USA to fully inform all students about health hazards associated with musical activities.  To better meet these requirements, additional research is needed to characterize both exposure levels generated during ensemble-based instructional activities and associated changes in hearing function.
This study was designed to address the National Institute for Occupational Safety and Health's (NIOSH) call for contemporary risk assessment techniques incorporating the 4 kHz frequency evaluation, and the recommended exposure limit of 8-h time weighted average of 85 dBA with an exchange rate of 3 dB. Although there is no universal widespread consensus on the one-to-one relationship between TTS and permanent threshold shift (PTS), it is well established that repeated exposure to high levels of noise usually leads to PTS. Since it is hard to induce or track PTS, TTS has been widely used in scientific research to study acute effects of noise knowing that TTS can in time become PTS. Hence, the purpose of our study was to determine if college students studying music (as opposed to non-music college students) are at an increased risk for hearing loss from temporary exposures to loud music (50 min), by tracking changes in basic audiometric measures.
The objectives of this study were: (1) Measure noise in a typical jazz band-based instructional activity that college music students are routinely exposed to, and in a regular classroom session that non-music students are routinely exposed to, and compare these noise levels to the daily permissible exposure limits set by NIOSH, and (2) Determine if music major students (experimental group), exposed to 50 min of jazz band practice sessions and non-music students (control group) exposed to 50 min regular classroom sessions showed significant differences between their pre- and post-exposure auditory measures.
| Methods|| |
This study involved two groups of college students. The experimental group consisted of 14 male students, majoring in music, routinely participating in jazz band-based practice sessions. The control group consisted of 11 male non-music major college students, who routinely attend regular classroom sessions. All participants signed an Institutional Review Board approved informed consent form.
| Case Report|| |
All subjects were asked to fill out a case history form prior to any audiological testing. Questions on the case history included identification information, hearing health queries such as possible hearing loss, ear aches, tinnitus and difficulty understanding speech. History of exposure to music and other types of loud noise were also included. The case history form was updated if there were any changes following the classroom session.
Pre-exposure auditory evaluations
All subjects underwent audiological testing that consisted of otoscopy, tympanometry, pure tone audiometry and otoacoustic emission (OAE) testing, specifically the TEOAEs. These test results, referred to as pre-exposure measures, were obtained from all subjects following a 24-h rest period which consisted of no exposure to loud noise of any kind, including music. All measures were obtained just prior to the start of the 50-min class session. Testing was conducted in a soundproof booth using calibrated equipment. Otoscopy was conducted using a Welch Allyn Otoscope. Tympanograms were obtained using a Maico MI-34 Impedance bridge. A GSI-17 audiometer was used to obtain pure tone air conduction thresholds from 250 kHz to 8 kHz. Tympanograms and hearing thresholds were obtained using standard clinical procedures. The Otodyanamics ILOv6 OAE system was used to obtain TEOAE measurements. Non-linear clicks of 75 dB sound pressure level (SPL) were used as the stimuli, with a noise-rejection level set to 49.5 dB SPL with stimulus stability at >95%. Response criterion adopted included reproducibility of greater than 50%, and amplitude response of greater than 3 dB SPL. 
Classroom noise measurements
Each participant wore a Quest Q-400 personal noise dosimeter during the scheduled 50-min classroom session. Using a clip, the dosimeter microphone was connected to the subject's shirt by investigators after subjects assumed their designated position in the ensemble/classroom. Microphones with wind screens were positioned half way between neck and shoulder, and aimed up. The microphone wire was positioned behind and down the back so as not to interfere with movement associated with performing musical instruments. Dosimeters and microphones were positioned on the right side of each subject except for trombonists because this instrument is positioned on the right shoulder. Subjects were instructed to perform/behave typically as they always do in the classroom, and were instructed not to touch or bump the microphone. The calibrated dosimeters were programmed for continuous automatic recording for 50 min with a threshold detection level of 40 dB SPL. The NIOSH (1998) recommended 3 dB exchange rate was used for calculation of equivalent sound level (L eq ). The dosimeters were also programmed to record the NIOSH dose. This reading gave the accumulated noise dose in percentage over a period of 50 min.
The noise recordings were made during routine 50 min jazz ensemble-based instructional activities. Like all ensemble-based instructional activities, the Professor facilitates learning through various means of communication that include verbal dialogue along with physical gestures. The timing, duration, and intensity level of verbal interaction are related to many factors including the daily and long term learning objectives and the instructional style of the professor. While verbal interactions may have occurred before, during, and following musical production, we measured the overall sound levels generated during class time. Our measurements only reflect all sounds generated during instruction and are not sufficient to determine details regarding the influence of dialogue on L eq or dose. Variability is expected across classes and instructors; hence, recordings were made at least twice per subject and averaged across the two sessions.
Post-exposure auditory evaluations
Following the 50-min class session (band-based instructional activity or regular classroom session), all subjects underwent another round of auditory evaluation within 10 min. Results from this testing session were referred to as post-exposure measures. Any change in the condition, such as tinnitus, during the post-evaluation period was recorded in the case history form. Tympanometry, pure tone audiometry and TEOAEs were repeated using the same equipment and soundproof booth as before. Statistical comparisons were made between pre-exposure measures and post-exposure measures for pure tone air conduction thresholds at 4 kHz and total TEOAE amplitude responses. All subjects underwent a 2 nd round of testing during the same semester. The same procedures used in the first round of testing were adopted for the 2 nd round of testing.
| Results|| |
Only subjects with bilateral type A tympanograms during pre-exposure testing were included in the study. None of the subjects complained of ear aches, ear discharge or difficulty understanding speech. As shown in [Table 1], the experimental group (E1-E14) consisted of 1 drummer, 2 trumpet players, 4 saxophone players, and 7 trombone players. The mean age of the experimental group was 24 ± 3.9 years, with a range of 19-33 years. The experimental group's mean duration of music playing was 13.5 ± 3.8 years, ranging from 6 years to 20 years. Case history information indicated that nine experimental subjects reported tinnitus, which did not change after post-exposure. No new occurrences of tinnitus were reported after the classroom session or for the 2 nd round of testing. None of the subjects had worn hearing protective devices at any time. The control group consisted of 11 males who were non-music major students. The mean age of this group was 24.9 ± 1.9 years, with a range of 23-29 years. None of the subjects in the control group reported of tinnitus or exposure to loud noise.
|Table 1: Experimental group data, including subject age, instrument played, number of years of playing, number of hours practicing per week, and report of presence of tinnitus|
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Sound levels measurements
The seating arrangement during a typical jazz band-based practice session is shown in [Figure 1]. The personal dosimeter worn by subjects measured sound levels continuously during the class session for 50 min. L eq , a single number that represents the equivalent continuous noise level, recorded during band-based instructional activity was found to range from 95 dBA to 105.8 dBA with a mean of 99.5 ± 2.5 dBA. The L eq recorded during regular classroom sessions, where the control group was located, ranged from 46.4 dBA to 67.4 dBA with a mean of 49.9 ± 10.6 dBA. Four subjects in the control group did not receive an L eq measure because the average sound level in the classroom was lower than the cutoff level of 40 dB SPL.
|Figure 1: The seating arrangement of music students during a typical jazz band-based practice session|
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Readings from the dosimetric measurement of dose (in percent) indicated that the sound levels generated during the 50 min periods of jazz instruction exceeded the daily limit set by NIOSH, but not during regular classroom sessions. [Table 2] depicts the averaged L eq data for each subject averaged across two rounds of testing. Conversion of the exposure levels to NIOSH daily dosage in percentage (displayed on the dosimeter) indicated that the experimental subjects had exceeded the daily dosage as a result of the noise levels generated in just one 50-min ensemble class session. This data is shown in [Figure 2] as "Event Dose". As seen from the graph, the experimental group exposure level from the averaged (across two sessions) 50-min practice event ranged from 100.1% to 825%, clearly exceeding the 100% daily dosage limit. The control subject exposure levels were well below the exposure limit (data not shown).
|Figure 2: Mean "Event dose" with reference to National institute for occupational safety and health's daily exposure in experimental subjects|
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|Table 2: Equivalent sound exposure levels (Leq) in dBA (decibel time-weighted) during the 50-min class session for experimental (a) and control subjects (b)|
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| Audiological Evaluation Results|| |
All participants had normal otoscopic findings and type a tympanograms in both ears. Pre-exposure testing revealed that all subjects had normal hearing between 250 Hz and 8 kHz, with the exception of one experimental subject who exhibited a threshold of 30 dB Hearing Level (HL) at 6 kHz in the left ear. [Table 3] shows the mean pre-exposure pure tone thresholds for experimental and control groups for 4 kHz pure tone and total TEOAE amplitudes.
|Table 3: Pre-exposure pure tone thresholds at 4 kHz and total TEOAE amplitudes|
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Difference between pre- and post-exposure sessions
The differences in pre- and post-exposure results are shown in [Figure 3]. The experimental group demonstrated an increase (shift) of 1.9 ± 1.01 dB HL in the right ear pure tone threshold and an increase of 4.1 ± 0.92 dB HL in the left ear pure tone threshold following the ensemble-based practice session. The control group showed a decrease in pure tone threshold of 1.4 ± 0.98 dB HL in the right and a decrease of 2.3 ± 1.7 dB HL in the left ear following the regular classroom session. The TEOAEs in the experimental group following post-ensemble practice were weaker by 1.6 ± 0.24 dB SPL in the right ear and 1.9 ± 0.5 dB SPL in the left. In the control group, the TEOAEs increased by 0.5 ± 0.44 dB SPL and 0.3 ± 0.35 dB SPL for right and left ears respectively.
|Figure 3: Mean and SE scores depicting change between pre- and post-exposure testing in experimental and control groups for right and left ears. *Indicates significant difference (P < 0.05). (a) Pure tone threshold shift at 4 kHz, and (b) total Transient-evoked otoacoustic emission amplitude reduction|
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Using independent samples t-test, mean scores from both groups were compared for differences between pre- and post-session audiological measures. Two-tailed significant differences (P < 0.05) were found between experimental and control subjects for (1) pure tone threshold at 4 kHz in right and left ears, and (2) TEOAEs in right and left ears. To identify if there was a correlation between the measured sound pressure level recorded in experimental subjects and their pure tone threshold shift and/or TEOAE change, we used Pearson product moment correlation measures. No significant relationships were found between sound exposure level and pre- and post-session hearing threshold shifts or TEOAE changes (correlation not significant at the 0.05 level, 2-tailed).
| Discussion and Conclusions|| |
The study was designed to determine if college students participating in jazz band instructional activities are at an increased risk for hearing loss compared to non-music students exposed routinely to regular classroom activities. The study quantified equivalent noise levels generated during jazz ensemble-based instructional activity and regular classroom activity in a university setting. The average L eq exposure level measured during the ensemble class was 99.5 dBA, which is comparable with several earlier studies that have reported equivalent noise exposure levels in musicians and DJs. , In our study, the range of L eq that the experimental group was exposed to was 95-105.8 dBA. This is similar to the results published in earlier studies that have reported sound levels ranging from 83 dBA to 112 dBA during music practice and rehearsal sessions by classical musicians. ,, In this study, contrary to the loud noise exposure in experimental subjects, the non-music control subjects in regular classrooms were exposed to sound levels that were well below 85 dBA. In four regular classrooms, the noise levels were so low (<40 dB SPL) that the dosimeter made no recordings.
Although earlier studies have documented poorer baseline audiometric thresholds and weaker TEOAE responses in musicians and DJs,  this study showed that all but one experimental subject had normal hearing. In actual fact, the mean pre-exposure pure tone thresholds for right and left ears at 4 kHz were better for the experimental group compared to the control group. Likewise, the mean pre-exposure TEAOEs in the experimental group were comparable or stronger than the mean pre-exposure TEOAEs from the control group. However, post-exposure measures indicated significant shift of pure tone thresholds in right and left ear at 4 kHz for the experimental group. This shift in threshold is thought to be temporary in nature, since follow-up testing done a week later in half of the group did not show the shift (data not shown). The total TEOAE measures were significantly weaker (lower) following the 50-min ensemble-based practice sessions for the experimental group.
Tinnitus is often associated with noise-induced hearing,  and in our study the incidence of tinnitus in the experimental group was much higher than in the control group. Of the 14 subjects in the experimental group, nine subjects (64%) reported of tinnitus at pre-exposure testing condition. Tinnitus is considered an early indication of possible damage to hearing.  Although there were no new reports of tinnitus following the ensemble-based practice session, the high incidence of tinnitus in the experimental group is remarkable. None of the subjects in the control group had tinnitus before or after their classroom sessions.
Exposure to noise, even temporarily, can lead to physical changes in cellular system in the cochlea and auditory neurons resulting in TTS. The main mechanisms of TTS include direct mechanical trauma to the organ of corti that houses the hair cells and metabolic stress due to increased oxidative mechanism.  Repeated TTS can lead to permanent cell damage  resulting in PTS. It has been known for a long time that TTS is a good indicator of PTS.  Hence, repeated exposure to loud music levels over the years among music students can by far lead to permanent loss.
This study showed that university students participating in jazz ensemble instructional activities are exposed to music (noise) levels that can exceed the daily dosage limit recommended by NIOSH, and exhibit temporary auditory changes following routine ensemble-based practice sessions. Sustained exposures to these levels could place these students at a greater risk for permanent sensorineural hearing loss. The significant TTS at 4 kHz and a decrease in total TEAOEs suggest subclinical damage to the auditory system from just 50 min of routine ensemble-practice sessions. While the daily doses measured in this study ranged from 100.1% to 825%, the study design was not sufficient to generalize these levels to the specific course, other classes within the same semester, or the instructors involved. Pervious research with concert band instructional activities showed that exposure levels do fluctuate from day-to-day, are different across instructors, and are related to pedagogic factors.  Similar research is needed for the jazz ensemble setting in order to better understand exposure levels associated with this type of ensemble-based instructional activity. Nevertheless, the overall mean exposure level of 99.5 dBA, (range 95-105.8 dBA) measured during the 50 min jazz band-based practice session exceeded the daily dose limit set by NIOSH, and appears to place those music students at a higher risk for hearing loss.
| Conclusion|| |
For college students majoring in music, participation in ensembles is a key and often required component of training and education. Basic criteria for accreditation by the NASM require that schools of music offer instruction in and opportunities for ensemble participation. This study showed that exposure levels generated during a jazz ensemble instruction activity can exceed the daily dose limit and those participating students' exhibit small but significant temporary changes in basic auditory measures, which can potentially lead to permanent hearing loss over a period of time. It is strongly recommended that music educators increase their efforts to understand the specific sound levels generated during ensemble instruction, fully inform students of risk levels, and to apply teaching strategies designed to prevent or minimize the risk of hearing loss on behalf of students.
| Acknowledgments|| |
This study was supported by the UNT Faculty Development Program award to KVG, and the UNT Internal Grant award to KC.
| References|| |
|1.||Carlsson PI, Van Laer L, Borg E, Bondeson ML, Thys M, Fransen E, et al. The influence of genetic variation in oxidative stress genes on human noise susceptibility. Hear Res 2005;202:87-96. |
|2.||Morata TC. Young people: Their noise and music exposures and the risk of hearing loss. Int J Audiol 2007;46:111-2. |
|3.||Schmuziger N, Patscheke J, Probst R. Hearing in nonprofessional pop/rock musicians. Ear Hear 2006;27:321-30. |
|4.||Zhao F, Manchaiah VK, French D, Price SM. Music exposure and hearing disorders: An overview. Int J Audiol 2010;49:54-64. |
|5.||Chesky K. Preventing music-induced hearing loss. Music Educ J 2008;94:36-41. |
|6.||Chesky K. Schools of music and conservatories and hearing loss prevention. Int J Audiol 2011;50:S32-7. |
|7.||Kähärit K, Zachau G, Eklöf M, Sandsjö L, Möller C. Assessment of hearing and hearing disorders in rock/jazz musicians. Int J Audiol 2003;42:279-88. |
|8.||Royster JD, Royster LH, Killion MC. Sound exposures and hearing thresholds of symphony orchestra musicians. J Acoust Soc Am 1991;89:2793-803. |
|9.||McBride D, Gill F, Proops D, Harrington M, Gardiner K, Attwell C. Noise and the classical musician. BMJ 1992;305:1561-3. |
|10.||Laitinen HM, Toppila EM, Olkinuora PS, Kuisma K. Sound exposure among the Finnish National Opera personnel. Appl Occup Environ Hyg 2003;18:177-82. |
|11.||Emmerich E, Rudel L, Richter F. Is the audiologic status of professional musicians a reflection of the noise exposure in classical orchestral music? Eur Arch Otorhinolaryngol 2008;265:753-8. |
|12.||Sadhra S, Jackson CA, Ryder T, Brown MJ. Noise exposure and hearing loss among student employees working in university entertainment venues. Ann Occup Hyg 2002;46:455-63. |
|13.||Opperman DA, Reifman W, Schlauch R, Levine S. Incidence of spontaneous hearing threshold shifts during modern concert performances. Otolaryngol Head Neck Surg 2006;134:667-73. |
|14.||Ostri B, Eller N, Dahlin E, Skylv G. Hearing impairment in orchestral musicians. Scand Audiol 1989;18:243-9. |
|15.||Mansfield JD, Baghurst PA, Newton VE. Otoacoustic emissions in 28 young adults exposed to amplified music. Br J Audiol 1999;33:211-22. |
|16.||Schmuziger N, Patscheke J, Probst R. An assessment of threshold shifts in nonprofessional pop/rock musicians using conventional and extended high-frequency audiometry. Ear Hear 2007;28:643-8. |
|17.||Behar A, MacDonald E, Lee J, Cui J, Kunov H, Wong W. Noise exposure of music teachers. J Occup Environ Hyg 2004;1:243-7. |
|18.||Petrescu N. Loud music listening. Mcgill J Med 2008;11:169-76. |
|19.||Chesky K, Dawson W, Manchester R. Health promotion in schools of music: Initial recommendations for schools of music. Med Probl Perform Art 2006;21:142-4. |
|20.||National Center for Chronic Disease Prevention and Health Promotion: Noise induced hearing loss. Atlanta: CDC; 2009. Available from: http://www.cdc.gov/HealthyYouth/noise/index.htm. [Last accessed on 2013 Mar 11]. |
|21.||National Association for Music Education: Health in music education (position statement). Reston, VA:. Available from: http://menc.org/about/view/health-in-music-education-positionstatement. [Last accessed on 2013 Mar 11]. |
|22.||Reid AR, Holland MW. A Sound Ear II: The Control of Noise at Work Regulations 2005 and Their Impact on Orchestras. London: Association of British Orchestras; 2008. Available from: http://www.abo.org.uk/user_files/ABO%20Publication%20Downloads/ASoundEarII.pdf. [Last accessed on 2013 Mar 11]. |
|23.||Sound Advice: Schools and Colleges: What you need to know. Sound Advice, 2007. Available from: http://www.soundadvice.info/schoolsandcolleges/schoolsandcolleges-step1.htm. [Last accessed on 2013 Mar 11]. |
|24.||National Association of Schools of Music: Handbook 2011-12. Available from: http://nasm.arts-accredit.org/site/docs/Handbook/ NASM_HANDBOOK_2011-12.pdf. [Last accessed on 2013 Mar 11]. |
|25.||Kemp DT. Otoacoustic emissions, their origin in cochlear function, and use. Br Med Bull 2002;63:223-41. |
|26.||Chesky K. Measurement and prediction of sound exposure levels by university wind bands. Med Probl Perform Art 2010;25:29-34. |
|27.||Bray A, Szymañski M, Mills R. Noise induced hearing loss in dance music disc jockeys and an examination of sound levels in nightclubs. J Laryngol Otol 2004;118:123-8. |
|28.||WHO. Prevention of Noise Induced Hearing Loss, WHO-PDH Informal Consultation, Geneva: World Health Organization; 1997. |
|29.||Rice CG, Rossi G, Olina M. Damage risk from personal cassette players. Br J Audiol 1987;21:279-88. |
|30.||Henderson D, Bielefeld EC, Harris KC, Hu BH. The role of oxidative stress in noise-induced hearing loss. Ear Hear 2006;27:1-19. |
|31.||May JJ. Occupational hearing loss. Am J Ind Med 2000;37:112-20. |
|32.||Luz GA, Fletcher JL, Fravel WJ, Mosko JD. The relation between temporary threshold shift and permanent threshold shift in rhesus monkeys exposed to impulse noise. Acta Otolaryngol Suppl 1973;312:1-15. |
Kamakshi V Gopal
P.O. Box 305010, University of North Texas, Denton, TX 76203-5010
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]