Recreational Noise Exposure Research Articles

The prevalence and characteristics of tinnitus in the youth population of the United States

To evaluate the prevalence, characteristics, and associated risk factors of tinnitus in U.S. adolescents. Cross-sectional analyses of U.S. representative demographic and audiometric data, the National Health and Nutrition Examination Survey (NHANES) 2005 to 2008. The study population consisted of 3,520 individuals aged 12 to 19 years with complete tinnitus-related data. Tinnitus was defined as the presence of ringing or buzzing in the ears lasting for at least 5 minutes during the preceding 12 months. In addition, we defined a chronic tinnitus subgroup as being bothered by tinnitus for more than 3 months. Demographic and other data regarding tinnitus, smoking, body mass index (BMI), anemia, hypertension, history of ear infections, tympanostomy tube placement, otoscopy, tympanometry and hearing thresholds, history of firearm use, and recreational and occupational exposure to noise were extracted and analyzed. Overall, tinnitus lasting 5 minutes or more in the preceding 12 months was reported by 7.5% of the 12- to 19-year-old population. This represents about 2.5 million adolescents in the United States. The prevalence of chronic tinnitus was 4.7%, corresponding to about 1.6 million adolescents in the United States. Multivariable-adjusted analysis revealed that both overall and chronic tinnitus were associated with female gender, low income, exposure to passive smoking, type A tympanogram, and occupational and recreational noise exposure. History of ≥ 3 ear infections and history of tympanostomy tube placement were associated only with overall tinnitus. Tinnitus afflicts a substantial portion of the youth population. Further investigation of the association between tinnitus and the identified risk factors is warranted.

Occupational and Recreational Noise Exposure from Indoor Arena Hockey Games

Occupational and recreational noise exposures were evaluated at two sporting arenas hosting collegiate hockey games (Venue 1) and semi-professional hockey (Venue 2). A total of 54 personal noise dosimetry samples were taken over the course of seven home hockey games: 15 workers and 9 fans at Venue 1, and 19 workers and 11 fans at Venue 2. None of the sampled workers were overexposed to noise based on Occupational Safety and Health Administration criteria. However, 40% and 57% of workers at Venue 1 and 33% and 91% of fans at Venue 2 were overexposed based on ACGIH noise exposure criteria. Noise exposures for fans were significantly different between venues, but worker noise exposures between venues were not significantly different. In addition, extensive area noise monitoring was conducted at each venue to further characterize the stadium noise on a location-by-location basis. Mean equivalent sound pressure levels ranged from 81 to 96 dBA at Venue 1 and from 85 to 97 dBA at Venue 2. Mean noise peak levels ranged from 105 to 124 dBA at Venue 1, and from 110 to 117 dBA at Venue 2. These data reflect the potential for overexposure at indoor hockey events and are useful in characterizing occupational noise exposure of indoor arena support staff and may also provide a foundation for future noise control research in indoor sports arenas.

Effect of recreational noise exposure on hearing impairment among teenage students

Several studies have focused on the potential impact of children's hearing loss on learning and development. Recently, numerous teenage students have been found to be fond of listening to music on personal devices and participating in recreational music activities. The objective of this study was to investigate teenage students' hearing impairment, their experience with recreational noise exposure, and their self-reported hearing. The participants were 1878 first-year students at a university in Taiwan. The result of the pure tone audiometry test showed that 11.9% of the participants had one or two ears with a hearing threshold over 25 dB. Over the past year, approximately 80.9% of the participants had taken part in at least one loud-noise recreational activity, and 90.9% of the participants were in the habit of using earphones. Among the participants, 190 students with a high level of recreational noise exposure were assigned to the exposure group, and 191 students with a low level of recreational noise exposure constituted the control group. The exposure group had more hearing problems than the control group, but no significant difference existed between the two groups in the pure tone audiometry test (p=0.857). It is suggested that the schools should reinforce hearing health education and proactively provide intervention measures, such as hearing tests, evaluation of noise exposure, and hearing protection.

Comparison of User Volume Control Settings for Portable Music Players with Three Earphone Configurations in Quiet and Noisy Environments

Listening to music is one of the most common forms of recreational noise exposure. Previous investigators have demonstrated that maximum output levels from headphones can exceed safe levels. Although preferred listening levels (PLL) in quiet environments may be at acceptable levels, the addition of background noise will add to the overall noise exposure of a listener. Use of listening devices that block out some of the background noise would potentially allow listeners to select lower PLLs for their music. Although one solution is in-the-ear earphones, an alternative solution is the use of earmuffs in conjunction with earbuds. There were two objectives to this experiment. The first was to determine if an alternative to in-the-ear earphones for noise attenuation (the addition of earmuffs to earbuds) would allow for lower PLLs through a portable media player (PMP) than earbuds. The second was to determine if a surrounding background noise would yield different PLLs than a directional noise source. This was an experimental study. Twenty-four adults with normal hearing. PLLs were measured for three earphone configurations in three listening conditions. The earphone configurations included earbuds, canal earphones, and earbuds in combination with hearing protection devices (HPDs). The listening conditions included quiet, noise from one loudspeaker, and noise from four surrounding loudspeakers. Participants listened in each noise and earphone combination for as long as they needed to determine their PLL for that condition. Once the participant determined their PLL, investigators made a 5 sec recording of the music through a probe tube microphone. The average PLLs in each noise and earphone combination were used as the dependent variable. Ear canal level PLLs were converted to free-field equivalents to compare to noise exposure standards and previously published data. The average PLL as measured in the ear canal was 74 dBA in the quiet conditions and 84 dBA in the noise conditions. Paired comparisons of the PLL in the presence of background noise for each pair of earphone configurations indicated significant differences for each comparison. An inverse relationship was observed between attenuation and PLL whereby the greater the attenuation, the lower the PLL. A comparison of the single noise source condition versus the surrounding noise condition did not result in a significant effect. The present work suggests that earphones that take advantage of noise attenuation can reduce the level at which listeners set music in the presence of background noise. An alternative to in-the-ear earphones for noise attenuation is the addition of earmuffs to earbuds.

Computer-based hearing loss prevention education program for Veterans and military personnel

INTRODUCTION According to the Veterans Benefits Administration, more than 672,000 Veterans were service-connected for hearing loss and more than 744,000 Veterans were service-connected for tinnitus as of fiscal year 2010 [1]. Hearing loss and tinnitus are the most prevalent disabilities experienced by Veterans who served during peacetime, Operation Iraqi Freedom/Operation Enduring Freedom, World War II, and the Korean war. In fiscal year 2010, the Department of Veterans Affairs (VA) provided 561,212 hearing aids at an estimated cost of $196.7 million and audiological services to Veterans at a cost of $227.4 million. * Therefore, hearing loss and tinnitus prevention should be a priority for the VA. At least one type of hearing loss--noise-induced hearing loss (NIHL)--can be prevented if appropriate protective strategies are implemented. Citing the high prevalences of hearing loss and tinnitus among Veterans, Fausti et al. concluded that programs aimed at preventing hearing loss should include education concerning the effects of both occupational and recreational noise exposures, as well as counseling on the hearing protection methods available to individuals at risk for NIHL [2]. Subsequently, authors Saunders and Griest worked with a video production company (Craftmaster Productions; Portland, Oregon) to implement this recommendation by developing a computer-based hearing loss prevention program (HLPP) for Veterans that could be accessed by patients in VA medical clinics [3]. HEARING LOSS PREVENTION PROGRAM The HLPP uses the constructs described in the Health Belief Model (HBM) developed by Rosenstock [4] to explain individual differences in decisions to practice particular health behaviors. To varying degrees, the HBM predicts health-related behaviors, such as prenatal care visits [5], breast cancer self-examination [6], continued enrollment in diabetes-related pharmaceutical services [7], and hepatitis B vaccination [8]. The principles outlined in the HBM were described by Folmer et al. [9, p. 12] as follows: 1. Susceptibility: The feeling of being vulnerable to a condition and the extent to which the individual believes he/she is at risk of acquiring the condition. 2. Perceived Severity: Belief in the seriousness of the consequences incurred if [a person is] affected by the condition both medically (e.g. death, disability, pain) and socially (e.g. effects on family life, personal relations). 3. Perceived Benefits: The belief that intervention will result in positive benefits. 4. Perceived Barriers: The barriers an individual believes he/she needs to overcome in order to effectively conduct some form of intervention. This includes costs, negative side effects, social stigma, and time needed for implementation. 5. Perceived Efficacy: Belief the individual has that he/she can successfully use the intervention. 6. Cue to Action: A cue that prompts an individual to take action. This could be internal, such as symptoms of a health problem, or external, such as media communications, interpersonal communications, or information from healthcare providers. One goal of the HLPP is to increase participants' knowledge about auditory system damage that can be caused by loud sounds and methods of hearing protection, which in turn would change participants' understanding and attitudes about noise exposure and hearing protection. The ultimate goal of this, and all HLPPs, is to motivate participants to change their behaviors in noisy situations so they implement appropriate hearing protection strategies. Most Veterans were exposed to loud sounds during their military service. Additional unprotected noise exposure will contribute to hearing loss in this population. Indeed, evidence exists that ears with prior noise damage age differently than those without significant noise exposure. Specifically, hearing loss progresses more quickly in noise-exposed ears than in ears not exposed to noise and loud sounds cause greater damage to already-exposed ears [10]. …

Occupational and recreational noise exposures at stock car racing circuits: An exploratory survey of three professional race tracks

Noise in stock car racing is accepted as a normal occurrence but the exposure levels associated with the sport have not been adequately characterized. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted an exploratory assessment of noise exposures to drivers, racing team members, and spectators at three stock car racing events. Sound level measurements were conducted using sound level meters, personal noise dosimeters, and a digital audio tape recorder that made sound recordings for later laboratory analysis. Area sound level measurements were made during race preparation, practice, qualification, and competition. Personal dosimetry measurements were conducted on drivers, team members, and spectators. Findings showed time-weighted averages (TWA) that ranged from A-weighted 96 decibels (dBA) for a spectator in the stands during a race to 114 dBA for a driver inside a car during practice. Peak sound pressure levels exceeded the maximum allowable limit of 140 dB during race competitions. Personal exposure measurements exceeded the NIOSH recommended exposure limit of 85 dBA as an 8-hr TWA in less than a minute for one driver during practice, within several minutes for team members, and less than one hour for spectators during the race. Hearing protection use was variable and intermittent among team members and spectators. Among drivers and team members, there was greater concern for communication performance than for hearing protection.

What Makes a Successful Hearing Conservation Program?

Although preventable, hearing impairment is one of the most prevalent disabilities in Western societies. In the United States, approximately 30 million individuals are at risk for noise-induced hearing loss and 22 million individuals between the ages of 20 and 69 have permanently damaged their hearing by exposure to loud sounds or noise in their environment. Both work-related and recreational noise exposure affect an individual's hearing. Legislation in 1969 and later in 1983 established standards mandating that all workers exposed to noise levels at or greater than 85 dBA time-weighted average be placed in a hearing conservation program that includes provision of hearing protective devices. This article discusses components of an effective hearing conservation program, and the roles and functions of interdisciplinary team members in making a hearing conservation program successful.

What Makes a Successful Hearing Conservation Program?

Although preventable, hearing impairment is one of the most prevalent disabilities in Western societies. In the United States, approximately 30 million individuals are at risk for noise-induced hearing loss and 22 million individuals between the ages of 20 and 69 have permanently damaged their hearing by exposure to loud sounds or noise in their environment. Both work-related and recreational noise exposure affect an individual's hearing. Legislation in 1969 and later in 1983 established standards mandating that all workers exposed to noise levels at or greater than 85 dBA time-weighted average be placed in a hearing conservation program that includes provision of hearing protective devices. This article discusses components of an effective hearing conservation program, and the roles and functions of interdisciplinary team members in making a hearing conservation program successful.

Hearing loss in veterans and the need for hearing loss prevention programs

Currently, there are more than 445,000 veterans receiving compensation for hearing loss associated with military service, and 395,000 receiving compensation for service-related tinnitus. In addition to compensation payments, service-related hearing disorders cost the US Department of Veterans Affairs in terms of provision of hearing aids, hearing aid-related services, and clinical services at its 220 facilities nationwide. It is imperative that hearing conservation among military personnel and veterans be addressed. In this paper, we describe the rationale for and the development of a multimedia Hearing Loss Prevention Program aimed at preventing the progression of hearing loss among veterans associated with social, recreational, and nonmilitary occupational noise exposure. The program was developed based on the principles outlined in the Health Belief Model of Rosenstock (1966) and the Health Promotion Model of Pender et al. (2002).

Occupational and recreational noise exposures at stock car racing circuits

Noise in stock car racing is accepted as a normal occurrence but the exposure levels associated with the sport have not been adequately characterized. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted an exploratory assessment of noise exposures to drivers, pit crew, team staff, and spectators at three stock car racing events. Area measurements were made during race preparation, practice, qualification, and competition. Personal dosimetry measurements were conducted on drivers, crew members, infield staff, and spectators. Findings showed time-weighted averages (TWA) that ranged from 94 decibels A-weighted (dBA) for spectators to 114 dBA for car drivers. Peak sound-pressure levels exceeded the maximum allowable limit of 140 decibels (dB) during race competitions. Personal exposure measurements exceeded the NIOSH recommended exposure limit (REL) of 85 dBA as an 8-h TWA in less than a minute for one driver during practice, within 2 min for pit crew and infield staff, and 7 to 10 min for spectators during the race. Hearing protection use was variable and intermittent among crew, staff, and spectators. Among drivers and crew, there was greater concern for communication performance than for hearing protection.

Trends in the Prevalence of Hearing Loss Among Young Adults Entering An Industrial Workforce 1985 to 2004

Studies have suggested that hearing loss due to recreational noise exposure may be on the rise among adolescents and young adults. This study examines whether the hearing status of young US adults entering an industrial workforce has worsened over the past 20 yr. The baseline audiograms of 2526 individuals ages 17 to 25 beginning employment at a multisite US corporation between 1985 and 2004 were analyzed to determine the yearly prevalence of hearing loss. Approximately 16% of the young adults in the sample had high frequency hearing loss (defined as hearing thresholds greater than 15 dB in either ear at 3,4, or 6 kHz). In a linear regression model, this prevalence decreased over the 20-yr period (odds ratio (OR) = 0.96, 95% confidence interval (CI): 0.94, 0.99). Almost 20% of subjects had audiometric "notches" consistent with noise exposure; this rate remained constant over the 20 yr, as did the prevalence (5%) of low frequency hearing loss. These results indicate that despite concern about widespread recreational noise exposures, the prevalence of hearing loss among a group of young US adults has not significantly increased over the past two decades.

The Use of Hearing Protection During Recreational Noise Exposure

The Use of Hearing Protection During Recreational Noise Exposure

The use of hearing protection devices by older adults during recreational noise exposure

A population-based study to assess the use of hearing protection devices by older adults during noisy recreational activities was performed. The population-based Epidemiology of Hearing Loss Study was designed to measure the prevalence of hearing loss in adults residing in Beaver Dam, Wisconsin. The use of hearing protection devices during noisy recreational activities was assessed by performing three examinations over a period of 10 years (1993-1995, no. of participants (n)=3753, aged 48-92 years; 1998-2000, n=2800, aged 53-97 years; 2003-2005, n=2395, aged 58-100 years). The recreational activities included hunting, target shooting, woodworking/carpentry, metalworking, driving loud recreational vehicles, and performing yard work using either power tools or a chain saw. The prevalence of using hearing protection devices during any of these activities increased with time (9.5%, 15.0%, and 19.9% at baseline, 5 years, and 10 years, respectively). However, the use of hearing protection devices remained low for most activities. Those under the age of 65 were twice as likely to use hearing protection devices during noisy activities than were older adults. Men, those with a hearing handicap, and those with significant tinnitus were more likely to use hearing protection devices. Smokers and the less educated were less likely to use hearing protection devices. The results demonstrated that many adults expose themselves to potentially damaging recreational noise, leaving them at risk for hearing loss.

Recreational noise exposure and its effects on the hearing of adolescents. Part I: An interdisciplinary long-term studyExposición a ruido recreativo y sus efectos en la audición de los adolescentes. Parte I: un estudio interdisciplinario a largo plazo

This interdisciplinary long-term study examined the effects of recreational noise exposure on the hearing of adolescents. Boys and girls (aged 14–17 years) were examined during a four–year period. Audiological, psychosocial, and sound measurements were performed yearly to determine the hearing threshold level (HTL) of participants in the 250–16 000 Hz range, their participation in recreational activities, and the sound levels at discos and through personal music player use. A tendency of the mean HTL to increase in both genders during the study was observed, especially at 14 000 Hz and 16 000 Hz. Boys had a higher mean HTL than girls. The participation in musical activities increased yearly, ’attendance at discos’ being the favourite musical activity for both groups. In general, boys were more exposed to high sound levels than girls. The equivalent sound levels in discos ranged between 104.3 and 112.4 dBA, and between 75 and 105 dBA from personal music players.

Hearing health and care: The need for improved hearing loss prevention and hearing conservation practices

Hearing loss affects 31 million Americans, particularly veterans who were exposed to harmful levels of noise during military functions. Many veterans also receive treatment with ototoxic medications, which may exacerbate preexisting hearing loss. Thus, hearing loss is the most common and tinnitus the third most common service-connected disability among veterans. Poor implementation of hearing protection programs and a lack of audiometric testing during medical treatment leave veterans vulnerable to unrecognized and untreated hearing loss until speech communication is impaired. Individualized audiometric testing techniques, including assessment of high frequencies, can be used in clinical and occupational settings to detect early hearing loss. Antioxidants also may alleviate cochlear damage caused by noise and ototoxicity. Ultimately, hearing loss prevention requires education on reducing occupational and recreational noise exposure and counseling on the risks and options available to patients. Technological advances will improve monitoring, allow better noise engineering controls, and lead to more effective hearing protection.

Output Levels of Commercially Available Portable Compact Disc Players and the Potential Risk to Hearing

To measure the sound levels generated by the headphones of commercially available portable compact disc players and provide hearing healthcare providers with safety guidelines based on a theoretical noise dose model. Using a Knowles Electronics Manikin for Acoustical Research and a personal computer, output levels across volume control settings were recorded from headphones driven by a standard signal (white noise) and compared with output levels from music samples of eight different genres. Many commercially available models from different manufacturers were investigated. Several different styles of headphones (insert, supra-aural, vertical, and circumaural) were used to determine if style of headphone influenced output level. Free-field equivalent sound pressure levels measured at maximum volume control setting ranged from 91 dBA to 121 dBA. Output levels varied across manufacturers and style of headphone, although generally the smaller the headphone, the higher the sound level for a given volume control setting. Specifically, in one manufacturer, insert earphones increased output level 7-9 dB, relative to the output from stock headphones included in the purchase of the CD player. In a few headphone-CD player combinations, peak sound pressure levels exceeded 130 dB SPL. Based on measured sound pressure levels across systems and the noise dose model recommended by National Institute for Occupational Safety and Health for protecting the occupational worker, a maximum permissible noise dose would typically be reached within 1 hr of listening with the volume control set to 70% of maximum gain using supra-aural headphones. Using headphones that resulted in boosting the output level (e.g., insert earphones used in this study) would significantly decrease the maximum safe volume control setting; this effect was unpredictable from one manufacturer to another. In the interest of providing a straightforward recommendation that should protect the hearing of the majority of consumers, reasonable guidelines would include a recommendation to limit headphone use to 1 hr or less per day if using supra-aural style headphones at a gain control setting of 60% of maximum.

Longitudinal threshold changes in older men with audiometric notches

Age-related hearing loss (presbycusis) is a multifactorial process that results chiefly from the accumulating effects of noise damage and aging on the cochlea. Noise damage is typically evidenced clinically by a discrete elevation (notch) of the auditory thresholds in the 3–6 kHz region of the audiogram whereas aging affects the highest frequencies first. To determine whether the presence of such high-frequency notches influences auditory aging, we examined the 15 year change in audiometric thresholds in 203 men from the Framingham Heart Study cohort. The mean age at the first hearing test was 64 years (range 58–80). Occupational and recreational noise exposure over the 15 years was assumed to be minimal due to the age of the subjects. The presence or absence of a notch was determined using a piecewise linear/parabolic curve fitting strategy. A discrete elevation of the pure-tone thresholds of 15–34 dB in the 3–6 kHz region was deemed a small notch (N1), and elevations of 35 dB or greater were deemed large notches (N2). Absence of a notch (N0) was encoded those ears with <15 dB elevation in the 3–6 kHz region. The presence and absence of notches correlated with the subjects’ history of noise exposure. The 15 year pattern of change in age-adjusted pure-tone thresholds varied significantly by notch category. There was less change over time in the notch frequencies (3–6 kHz) and significantly greater change in the adjacent frequency of 2 kHz in the N2 group as compared to the N0 and N1 groups. The adjacent frequency of 8 kHz showed a significant, but smaller, change in the N1 group as compared to the N0 and N2 groups. The change at 2 kHz was independent of the starting hearing level at E15, whereas the changes at 4–8 kHz were influenced by the hearing level at E15. These data suggest that the noise-damaged ear does not ‘age’ at the same rate as the non-noise damaged ear. The finding of increased loss at 2 kHz suggests that the effects of noise damage may continue long after the noise exposure has stopped. The mechanism for this finding is unknown but presumably results from prior noise-induced damage to the cochlea.

Noise-induced hearing loss in young adults: the role of personal listening devices and other sources of leisure noise.

No consensus exists regarding the magnitude of the risk of noise-induced hearing loss (NIHL) associated with leisure noise, in particular, personal listening devices in young adults. Examine the magnitude of hearing loss associated with personal listening devices and other sources of leisure noise in causing NIHL in young adults. Prospective auditory testing of college student volunteers with retrospective history exposure to home stereos, personal listening devices, firearms, and other sources of recreational noise. Subjects underwent audiologic examination consisting of estimation of pure-tone thresholds, speech reception thresholds, and word recognition at 45 dB HL. Fifty subjects aged 18 to 30 years were tested. All hearing thresholds of all subjects (save one-a unilateral 30 dB HL threshold at 6 kHz) were normal, (i.e., 25 dB HL or better). A 10 dB threshold elevation (notch) in either ear at 3 to 6 kHz as compared with neighboring frequencies was noted in 11 (22%) subjects and an unequivocal notch (15 dB or greater) in either ear was noted in 14 (28%) of subjects. The presence or absence of any notch (small or large) did not correlate with any single or cumulative source of noise exposure. No difference in pure-tone threshold, speech reception threshold, or speech discrimination was found among subjects when segregated by noise exposure level. The majority of young users of personal listening devices are at low risk for substantive NIHL. Interpretation of the significance of these findings in relation to noise exposure must be made with caution. NIHL is an additive process and even subtle deficits may contribute to unequivocal hearing loss with continued exposure. The low prevalence of measurable deficits in this study group may not exclude more substantive deficits in other populations with greater exposures. Continued education of young people about the risk to hearing from recreational noise exposure is warranted.

Pesticide illness surveillance: Review of the national pesticide hazard assessment program

Age-related hearing loss (presbycusis) is a multifactorial process that results chiefly from the accumulating effects of noise damage and aging on the cochlea. Noise damage is typically evidenced clinically by a discrete elevation (notch) of the auditory thresholds in the 3–6 kHz region of the audiogram whereas aging affects the highest frequencies first. To determine whether the presence of such high-frequency notches influences auditory aging, we examined the 15 year change in audiometric thresholds in 203 men from the Framingham Heart Study cohort. The mean age at the first hearing test was 64 years (range 58–80). Occupational and recreational noise exposure over the 15 years was assumed to be minimal due to the age of the subjects. The presence or absence of a notch was determined using a piecewise linear/parabolic curve fitting strategy. A discrete elevation of the pure-tone thresholds of 15–34 dB in the 3–6 kHz region was deemed a small notch (N1), and elevations of 35 dB or greater were deemed large notches (N2). Absence of a notch (N0) was encoded those ears with <15 dB elevation in the 3–6 kHz region. The presence and absence of notches correlated with the subjects’ history of noise exposure. The 15 year pattern of change in age-adjusted pure-tone thresholds varied significantly by notch category. There was less change over time in the notch frequencies (3–6 kHz) and significantly greater change in the adjacent frequency of 2 kHz in the N2 group as compared to the N0 and N1 groups. The adjacent frequency of 8 kHz showed a significant, but smaller, change in the N1 group as compared to the N0 and N2 groups. The change at 2 kHz was independent of the starting hearing level at E15, whereas the changes at 4–8 kHz were influenced by the hearing level at E15. These data suggest that the noise-damaged ear does not ‘age’ at the same rate as the non-noise damaged ear. The finding of increased loss at 2 kHz suggests that the effects of noise damage may continue long after the noise exposure has stopped. The mechanism for this finding is unknown but presumably results from prior noise-induced damage to the cochlea.

Effects of gunfire on hearing level for selected individuals of the Inter-Industry Noise Study.

Using the information available from Inter-Industry Noise Study, the hearing levels of 68 pairs of workers, matched for sex, age, and exposure level, were evaluated. For each pair, one of the participants had indicated exposure to nonoccupational gunfire during the previous year. Differences in mean hearing levels between the male participants exposed to gunfire and those not exposed were clearly apparent and varied between 9 to 16 dB for the frequencies at 3000, 4000, and 6000 Hz. There were no significant differences in female hearing threshold levels. These changes in male hearing are equivalent to the effect of an occupational exposure of 89 dB for 20 years. However the results do not indicate that there are any synergistic effects between gun exposures during a participants recreational time and noise exposure during his working hours.