Our research team took advantage of a “sample of convenience” to study the hearing of nearly 400 amateur and professional percussionists who attended the Percussive Arts Society International Conventions (PASIC) in Louisville, KY (2003) and Nashville, TN (2004). The Percussive Arts Society had offered its members hearing screenings for a number of years prior to our work, but it granted us wider access to the conventioneers for the purpose of conducting three projects. The main findings are summarized in this article.
When research is conducted on a sample of convenience, there is some risk that only those who suspect they have a problem (in this case, hearing loss) will volunteer as subjects, thus skewing the data. In an attempt to avoid this problem and increase the heterogeneity of the sample, volunteers were given a pair of Etymotic ER-15 musician-quality hearing protection devices (HPDs) and told they might be chosen for a “special test that could detect early damage to the inner ear” (otoacoustic emissions) as inducements to participate.
AUDITORY THRESHOLDS IN PERCUSSIONISTS
Previous research has shown that percussionists routinely produce peak sound pressure levels that exceed 120 dB.1 Drum rolls can create 106 dB (A) and single notes can reach 137 dB (A).1 Several studies have found percussionists to have the worst hearing thresholds of all musicians.2-4
It has been suggested that the intermittent loudness and highly variable intensity of music might reduce a musician's risk for hearing loss as compared with workers exposed to constant levels of damaging industrial noise.5 Music produced by percussionists typically contains more low-frequency energy than high,6 which has been thought to reduce their risk for hearing damage.
Kahler et al. assessed the hearing of rock and jazz musicians.7 Although their sample exhibited minimal differences in auditory thresholds when compared with ISO 7029 reference data, most of the subjects who fell outside the 90th percentile were percussionists. The purpose of the present study was to quantify auditory thresholds in a large sample of percussionists. We believe this represents the largest such study to focus exclusively on this population.
Among the 4000 percussionists who attended the 2003 PASIC event, 315 volunteered as subjects. They ranged in age from 18 to 75 years, with a mean of 30.9 years. Sixty-seven (67) were female, 240 were male, and 8 did not report their gender on our research consent forms.
We used calibrated Maico microprocessor audiometers with TDH-39 headphones to obtain pure-tone auditory thresholds. Testing was conducted in an IAC four-person sound-treated booth within a mobile trailer. Ambient sound pressure levels within the test environment were monitored at 4-hour intervals to assure compliance with the test standards. Subjects pre-qualified for testing by passing an otoscopic inspection and tympanometric screen. We measured pure-tone air-conduction thresholds by means of the Hughson-Westlake technique at 500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz.
We compared the mean auditory thresholds of the percussionists with the ISO 7029 (2000) reference data for otologically normal populations of the same age and gender distribution. For a given age and gender, the ISO standard provides the statistical distribution for the threshold deviations for an otologically normal person. In particular, the standard provides median values (ΔHmd, y) for these distributions. We used the formula ΔHmd, y = alpha (y-18 years)2 to calculate the median threshold for a given age and gender, i.e., to provide an otologically normal control reference for each subject in our sample.
Figures 1A and 1B illustrate the differences observed between the reference and percussionist populations. At all frequencies, the percussionists have poorer mean auditory thresholds than the reference group. These differences, which were slightly more pronounced in the left ears, range from 5 to 11 dB.
Mean thresholds for percussionists and the ISO reference population, along with mean group differences and the 95% confidence intervals, are displayed in Table 1. “Hearing loss” was defined as hearing thresholds ≥25 dB HL at two or more frequencies or ≥30 dB HL at one frequency in one or both ears. By this definition, the prevalence of hearing loss is 39% (119/304) in the percussionists group and 9% (28/304) in the age- and gender-matched ISO reference group.
The percussionists' conventions included a number of events that produced sound pressure levels with the potential to create temporary threshold shifts (TTS) in our study subjects. As this was a “sample of convenience” and because we were intent on obtaining a real-time “snap-shot” of percussionists' auditory sensitivity, we tested subjects who were and also subjects who were not exposed to loud sound in the context of the convention.
However, we had data that allowed us to determine the time interval between their last exposure to loud music and their threshold audiometry. We used these to analyze the effects of exposure to loud sound pressure levels during the convention. NIOSH (National Institute for Occupational Safety and Health) standard #98–126 for baseline hearing testing in occupational situations requires that employees have at least 12 hours free of significant noise exposure prior to threshold measurement.
Using this standard, we divided our subjects into two groups: those who met the NIOSH 12-hour rule immediately prior to threshold testing and those who did not. Analysis revealed no statistically significant difference between the mean auditory thresholds of the two groups (Hotelling's T2 Test: F14, 274=1.70, p=0.054). Therefore, we combined the data from the two groups and reported them in Figures 1A and 1B and Table 1 above. The resulting auditory threshold differences between percussionists and the derived ISO standard thresholds are considered valid.
Prior to testing, subjects said whether they used hearing protection devices (HPDs) “always,” “sometimes,” or “never.” Of the 291 percussionists who responded to this question with respect to using HPDs during performances, 33% (97) reported using them either always or sometimes.
Subjects reported using a wide range of HPD types, including “musician's,” “custom-made,” “foam,” and “other.” Analysis showed that those who said they sometimes or always wore some type of HPD had consistently better auditory thresholds than those who did not, although the differences did not reach the level of statistical significance. We suspect that the widely disparate styles and use patterns accounted for this fact.
To isolate the effect of using hearing protection, we analyzed the data separately from subjects who used the most commonly reported style, roll-up “foam” HPDs. Those who said they always or sometimes used them during practice sessions had significantly better auditory thresholds (p≤0.01). Table 2 shows mean thresholds for those who did and did not use foam HPDs. These differences are in the range of 2 to 4 dB across frequencies.
We also compared auditory thresholds of professional and amateur percussionists. A multivariate regression of threshold onto music career (i.e., professional or amateur), while controlling for age, gender, and HPD use, revealed that professionals had significantly poorer thresholds (in the range of 2 and 8 dB) between 2000 and 8000 Hz.
Fifty-four percent of the percussionists in our entire sample reported experiencing tinnitus “sometimes” or “always.” Professionals were more likely to have tinnitus (57.6%) than amateurs (44.2%). Note that tinnitus affects approximately 14% to 17% of the general population.8,9 Our sample showed no statistically significant correlation between the presence of tinnitus and either age, auditory thresholds, HPD use, gender, years of experience, or type of percussion instrument played.
EARLY EVIDENCE OF COCHLEAR DAMAGE*
We examined a normal-hearing subset of the percussionists attending the PASIC event in Louisville for early, “sub-clinical” signs of outer hair cell damage. For this phase of the study, we chose 86 subjects with auditory thresholds better than 25 dB HL in the range of 2000 to 8000 Hz. This group included 59 males and 27 females ranging in age from 18 to 52 years (mean = 26.9 years). Subjects who reported having been exposed to loud noise within the preceding 14 hours were excluded from the study.
We also studied a non-percussionist control group of 39 subjects without any significant history of noise exposure. They included 13 males and 26 females ages 21 to 51 years (mean = 25.9). As with the percussionists, the audiometric thresholds of the controls were better than 25 dB HL from 2000 to 8000 Hz. There was no statistically significant difference in mean pure-tone thresholds of the two groups or in their mean ages.
Persons with a family history of hearing loss, self-reported hearing loss, or neurologic problems, or who had abnormal otoscopic examinations or tympanometry were excluded from both groups of subjects.
We recorded distortion-product oto-acoustic emissions (DPOAEs) for both groups using a Bio-Logic Scout DPOAE system. The level for L1 was 65 dB and 55 dB for L2. The F2/F1 ratio was set to 1.22. F2 was measured at 1968, 3139, 3983, 6373, and 7966 Hz. To be considered a response, the DP amplitude had to be at least 3 dB greater than the noise floor.
Figure 2 depicts the mean DPOAE amplitudes for right and left ears of the normal-hearing percussionists and the control subjects. In both right and left ears of the normal-hearing percussionists, the DPOAE amplitudes are reduced relative to the control group. The percussionists' amplitudes are significantly lower than the controls' at 6000 Hz in both the left and right ears.
Figure 3 represents the prevalence of absent or non-recordable DPOAEs for the normal-hearing percussionists and the non-percussionist subjects when left and right measurements are combined. Although the observed differences are not statistically significant, there is a clear pattern suggesting that percussionists are more likely to have absent DPOAEs in the range of 3000–6000 Hz.
When all measurements are considered (i.e., all five frequencies in both ears), there is a statistically significant difference between groups. Forty-one of 755 (5.4%) measurements in percussionists produced an absent DPOAE, whereas 12 of 390 (3.1%) measurements from the controls revealed absent DPOAEs. This difference reached a level of statistical significance (p=0.047, Fisher's Exact Test).
We were interested in determining if the use of HPDs had any influence on the DPOAEs recorded from the normal-hearing percussionists. Percussionists who reported using HPDs “always” or “sometimes” had significantly better DPOAE amplitudes than those who “never” use protection. This difference reached a level of statistical significance at 6000 Hz in the left ears (p=0.01) and at 4000 Hz in the right ears (p=0.02).
Indeed, DPOAE amplitudes were an average of 7.3 dB SPL better at 6000 Hz in the left ear and 4.9 dB SPL better at 4000 Hz in the right ears of those who used HPDs. These findings suggest that “normal-hearing” percussionists, particularly those who never use HPDs, have more “sub-clinical” cochlear damage than do their non-noise exposed, normal-hearing peers.
Prevention of hearing loss is the primary aim of any hearing conservation program. Reduced OAE amplitudes and/or absent OAEs without “hearing loss” (as traditionally defined for screening purposes) is the first objective sign of outer hair cell damage. OAE measurements should be included in any hearing conservation program.
Doing so is especially important for musicians because their careers depend so heavily on their auditory skills. See the work of Attias and colleagues10-12 for more information about using OAEs to detect noise-induced hearing loss in so-called “normal-hearing” persons.
ATTITUDES TOWARD HEARING CONSERVATION
Our third study examined the attitudes and behaviors of percussionists regarding hearing conservation. It also attempted to measure their response to a brief (5–10 minute) educational intervention on the risks of music-induced hearing loss (MIHL) and HPD use. Our data were collected at both the 2003 and 2004 Percussive Arts Society Conventions.
We gave 400 of the percussionists at the Louisville event a brief educational intervention, which included information on the warning signs of hearing loss, the problems associated with MIHL, and the types of HPDs available for musicians and their relative benefits. A doctoral student conducted the sessions face-to-face with individual subjects or groups of two to four subjects.
Each subject received a take-home information packet. The first 300 subjects who heard the presentation also received a free pair of Etymotic ER-15 musician-quality HPDs. Subjects were told they would be mailed a follow-up survey 6 months later to inquire about their hearing. This survey, which was sent to the 350 subjects who attended the presentation and gave valid addresses, asked six questions concerning HPD compliance, reasons for HPD use or non-use, preferred type of HPD, and whether or not they had sought hearing care after hearing the educational presentation. About half the subjects (172 of 350) returned the completed survey.
We surveyed a second group of 111 randomly selected percussionists in a face-to-face interview format at the PASIC event in Nashville. None of them had participated in our research the previous year or heard our educational intervention in Louisville. These interviewees were asked 14 questions about HPD use, hearing conservation, and hearing loss.
The combined total of respondents from Louisville and Nashville was 283, 21% female and 79% male. They ranged in age from 8 to 69 years and 55% were from 18 to 29. The subjects had been either amateur or professional percussionists for 1 to 60 years; the modal number of years playing was in the range of 11–20 years.
Subjects reported using HPDs more often while practicing than performing. Sixty-seven percent used HPDs at least sometimes during practice, while 56% reported using HPDs at least sometimes during performances. Thirty percent reported purchasing some sort of HPD within the previous year. Of those reporting at least some HPD use, the majority (N=75) described the foam/flange type. Only 15% of respondents had had their hearing tested within the previous year.
Of the 172 subjects in the Louisville sample, a remarkable 77% (132) reported wearing HPDs “more often” after receiving the brief educational presentation at the PASIC event the previous year. When asked why, they said it was because they were more aware of the dangers of loud music (78%), were made aware of the benefits of musician-quality HPDs (76%), received a free pair of Etymotic ER-15 earplugs (77%), or learned that they were at risk for MIHL (44%).
Only 23% of these subjects said they did not use HPDs after the educational intervention. Their reasons included: “hassle” (33%), “sound quality” issues (25%), “denial of need” (22%), “cost” (15%), and “appearance” (5%).
Twenty-seven percent (46) purchased a new set of HPDs after hearing the educational program in Louisville. The most frequently purchased types were non-custom musician-quality (35%), followed by custom-made musician quality (29%), foam/flange (26%), headset (6%), and wax/molded (4%). Thirteen percent (22) consulted an audiologist or physician after receiving the results of the pure-tone threshold audiogram performed the previous year.
There were 1111 subjects in the Nashville sample, who were interviewed face-to-face. None had participated in the Louisville research the previous year.
Fifty-nine percent said they used HPDs while practicing and 44% when performing. Thirty-nine percent had purchased new HPDs within the previous year. Fifty-one percent reported using a foam/flange design, 16% wore a headset, 12% wore custom-made, musician-quality products, 11% used wax/molded types, and 10% wore non-custom, musician-quality HPDs.
Those who reported not wearing HPDs offered several reasons, including: “sound quality” issues (48%), “hassle” (34%), “denial of need” (9%), or “cost” (8%). None reported that “appearance” was a factor.
All the Nashville subjects, whether they used HPDs or not, were asked to list their advantages. Responses included: “could save my hearing” (96%), “prevent tinnitus/ringing in my ears” (59%), “make loud sounds more comfortable” (58%), “reduce loudness without causing distortion” (40%), and “prevent fatigue” (29%). Eighty-nine percent were aware that MIHL is permanent and irreversible. Nearly all (93%) knew that not all HPDs are equally effective for percussionists.
Alarmingly, despite knowing the benefits of HPDs, most subjects did not use them consistently and, when they did, most used industrial-style foam/flange devices rather than more effective musician-quality protection. In addition, 82% of our sample had not had a hearing test within the past year.
However, the data collected 6 months after the brief educational intervention in Louisville are more encouraging. They indicate that use of hearing protection increases when percussionists are reminded about the consequences of MIHL and also receive a free pair of musician-quality HPDs. Subsequent research might investigate whether the education or the free devices are more likely to improve compliance.
In any case, it seems appropriate to counsel percussionists of any age and level of experience to get annual audiologic evaluations, limit their exposure to loud sound, and wear HPDs routinely. This message should be reiterated at every opportunity (conventions, workshops, demonstrations), and especially by music educators.
The three related studies of percussionists' hearing and their use of protection show that their auditory thresholds are 5 to 11 dB worse than age- and gender-matched peers with no history of routine exposure to loud sound. The prevalence of hearing loss (PTA ≥25 db HL) is estimated to be 39% among percussionists, whereas in the general population it is approximately 9%.
Even when they did not have hearing loss, the percussionists appeared to be more subject to “sub-clinical” damage to the outer hair cells than a comparable sample of normal-hearing subjects without a history of exposure to loud noise or music. Among the percussionists, otoacoustic emissions were more often absent or reduced in amplitude than in the normal-hearing sample. Percussionists who use HPDs always or sometimes have significantly better OAEs than those who do not. It is recommended that OAE measurements be performed as a routine aspect of the audiologic evaluation for percussionists.
Although percussionists are generally aware of both the dangers of repeated exposure to loud music and the benefits of HPD use, their compliance in using these devices is disappointing. Evidence suggests, however, that a brief educational intervention can be effective in improving compliance. It seems reasonable to believe that once musicians experience the benefits of these devices, they will be likely to continue their use.
The authors are grateful for the cooperation of the Percussive Arts Society and its Health and Wellness Committee. They also thank Etymotic Research, Inc., for supplying 300 pairs of ER-15 musician-quality HPDs for this study.