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Figure.:
Warwick Williams, PhD
The possibility of leisure activities—especially listening to music on portable music players—causing hearing loss in young people never fails to excite the press. The many stories on this topic seem to reflect genuine concern in the population about this issue.
As this article by Warwick Williams, PhD, shows, however, this concern does not seem well founded for nearly all young people. This is not to say that leisure noise cannot cause hearing loss, but it certainly does not seem to be very common.
There are two caveats: First, recent analysis of the extensive data discussed by Dr. Williams has shown a significant relationship between total leisure-induced noise exposure and the occurrence of tinnitus, so it seems that noise exposure is indeed having some effects on the ears of some young people, even if it is not reflected in their hearing thresholds. These effects seem to occur even with accumulated noise doses much lower than those that would occur in a workplace with average daily levels of 85 dBA.
Second, the study that Dr. Warwick describes was carried out before we realized the importance of looking for the symptoms of “hidden hearing loss”—the loss of high-threshold nerve fibers that have no effect on hearing thresholds but probably contribute to the accurate analysis of sound at moderate or high noise levels. A new, large-scale study is now under way to explicitly look for these symptoms, one of which may well be an increased prevalence of tinnitus.
Although the study was done on an Australian population, ears are the same everywhere, and the types of devices that people use for music are international, so it seems likely that the results would apply to other populations. If so, then the safety message we have so far for other countries is that the most dangerous leisure noise activities seem to be dance parties.
For just a very small proportion of young people, the combination of high sound levels and exposures of several hours per outing repeated weekly for several years is certainly sufficient to provide noise exposure sufficient to damage hearing, even if the number who receive this much exposure is small.
—Harvey Dillon, PhD
Director
National Acoustic Laboratories
From time to time, articles appear in the popular press, and even in some academic journals, noting that with the increasing availability and performance of loud music and personal listening devices, the hearing health of listeners may be at risk; the implication is that this is affecting the younger members of the community, rather than older members. This is also frequently coupled with an urgent call to action to address the “bad listening habits” of these younger individuals.
Faced with increasing public and professional concerns that the hearing of young Australians was at risk, National Acoustic Laboratories (NAL) initiated a research study to examine the problem using the perspective of a cross-sectional survey. To this end, and with funding provided by the Australian Government Department of Health, a project titled Prevalence of Hearing loss and Its Relationship to Leisure-Sound Exposure was undertaken (“Prevalence of hearing loss and its relationship to leisure sound exposure.” National Acoustic Laboratorieshttp://www.hearingservices.gov.au/wps/portal/hso/site/about/whoarewe/research/hlpp_hearingloss_leisure_sound/!ut/p/a1/tZFNU4MwEIb_ipceM1kCFDhm-iWtbcexKnBhAg0kShPKh7X_3nTGHkV7cG-7886z7-6LExzhRLEPWbJOasWqS5-M09WjO7ZCICv_ZTsHSjfPD8u5Q2AL-BUnOMlVV3cCx6LVd7lWHVfdCOo-q2Q-AqEPfAQs070ZnoRmDT-ZQcNbzppcGEFV16kwjVRlpds2rbhs-4anre7V_sKvc7nHcTB2cw8sgryMFMgJAoYyvwiQZRM3cwrHs2BvDMfGMPxQFP50z4AE3G_BwIrYePBS4k_pfeBY4XYWzoBOFrvlwg_JYuripxuPGgbu4Gbg8rc3mDfKt-MxoSbcS6CfHY7-JV2ziDTrybo0_lknkFSFxtEVhKMryKwfBtWHg2-f0Xux2SCW-We7KukXw4trLA!!/dl5/d5/L2dBISEvZ0FBIS9nQSEh/).
The project commenced by recruiting young Australians between the ages of 11 and 17 years; however, when the initial examination of results did not show much indication of hearing loss, the upper age range of the study was extended to 35 years.
The testing included a detailed hearing health history and comprehensive audiometric evaluation, including otoscopy, tympanometry, air- and bone-conduction thresholds, and transient and distortion-product otoacoustic emissions (OAE). A detailed lifelong history of participation in noisy activities, including work, non-work, and leisure activities, was also gathered, along with standard demographic data.
The intent of gathering information on participation in noisy activities was to provide information that could be credibly used to make an estimate of an individual's cumulative lifetime noise exposure. In a parallel project, NAL concentrated on gathering typical noise levels and participation times arising from non-work and leisure noise activities. Multiple measures were made to produce average exposure levels and average exposure time.
Added to this was the frequency of participation, such as attendance times per week, per year, and so on, including over how many years the particular activity was pursued. Collating this information with participant responses from their individual activity surveys allowed us to make reasonable estimates of noise exposures for different activities.
These activity exposures can then be added to produce an estimate of a lifetime noise exposure profile (Noise Health 2010;12[48]:155-158http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=2010;volume=12;issue=48;spage=155;epage=158;aulast=Williams). The basic methodology is similar to that used in the International Organization for Standardization's “Acoustics—Estimation of noise-induced hearing loss” to estimate the daily A-weighted noise exposure, LEX,8h, with a creative extension to include lifetime noise exposure from all significant sources (“Estimation of noise-induced hearing loss. International Organization for Standardization.” 2013http://www.iso.org/iso/catalogue_detail.htm?csnumber=45103).
INITIAL NORMATIVE HEARING THRESHOLD LEVELS DEVELOPED
Results from our work lead us to believe that the lifetime exposure estimates we produce are a reasonable estimate of the true situation. If they are not precise, they will at least provide a first-order-of-magnitude estimate of the true situation.
Having gathered the data, considerable effort was expended to ensure that there were no irregularities or possible fallacious information. This process was followed by analysis and the preparation of various reports and scientific papers.
This first formal work was a detailed survey of the existing literature on leisure noise and hearing health ( Ear Hear 2014;35[5]:491-505http://journals.lww.com/ear-hearing/Abstract/2014/09000/The_Leisure_Noise_Dilemma___Hearing_Loss_or.1.aspx). This survey argued that there is a real risk of hearing damage from exposure to noisy leisure activities, but there is also much speculation as to the extent and depth of any actual effect.
After filtering for possible medical confounders, there were about 1,450 people who provided valid and useful data. Hearing status was not a selection criterion for participation; the only criteria were the specified age range and a willingness to participate. Participants came from high schools, universities, tertiary and further education colleges, and a variety of workplaces, including the government sector and private industry.
Initial results produced a useful set of hearing threshold reference levels from the ages of 12 to 35 years in two-, five-, and ten-year steps at fractiles of 0.1, 0.25, 0.5, 0.75, and 0.95 (Int J Audiol 2014;53[5]:289-293http://www.tandfonline.com/doi/abs/10.3109/14992027.2013.873957?journalCode=iija20). This work provided normative threshold levels applicable to the young Australian population—an important result, as such tables did not previously exist. Interestingly, there appears to be no such normative information on threshold levels for any population younger than 18.
A summary of the distribution of threshold levels for the 11- to 35-year-olds, men and women, is presented in the table.
TEST RESULTS DEFY SOME EXPECTATIONS
The audiometric test conditions complied with the requirements of International Standards for measuring down to 0 dB hearing threshold level (HTL) with an uncertainty of +5 dB (ISO 8253-1). This was managed by choosing a quiet location at the test site and the use of insert earphones covered by a noise-excluding headset (Acoust Au 2013;41[3]:232-233http://www.acoustics.asn.au/journal/2013/2013_41_3_Fisher.pdf). The fact that audiometric testing was carried out in situ and not at a specialized facility meant that measured thresholds could be guaranteed only down to 0 dB HTL.
The second significant result was to produce normative figures for OAEs, which currently do not exist for the Australian population—or, in fact, for any population (Int J Audiol 2015; July 8:1-12. [Epub ahead of print]http://www.tandfonline.com/doi/full/10.3109/14992027.2015.1046505). The tables we developed present transiently evoked OAE (TEOAE) amplitudes, signal-to-noise ratios (SNRs) (male, female, and combined), and diagonal peak (DP) amplitudes DP1 and DP2, all of which will be useful for practitioners requiring reference levels for comparison purposes.
The most important result of this study is that no measurable change in threshold levels with respect to age in the population of 11 to 35 years has been found—hearing thresholds remain well within what are considered normal levels, a result that runs counter to expectations.
There is also no statistically significant relationship between cumulative noise exposure and hearing thresholds for any of the tested frequencies (0.5 kHz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 6 kHz, and 8 kHz) across the sampled population, nor does such a correlation exist between OAEs and exposure levels.
This is not to say that leisure noise cannot cause hearing loss in people who have high average exposures; it is just that it does not appear to be as widespread a problem in society as has been feared by many. The concern is thus that reaction to this reported problem has the potential to divert attention and detrimentally alter more appropriate hearing health messages.
In summary, the results to date do not support the hypothesis that there is an increase in the rate of measurable hearing loss in young people in Australia in relation to any apparent increase in the availability of non-work and leisure noise exposure from amplified music or the use of personal music players.
