Symphony orchestra musicians' use of hearing protection and attenuation of custom-made hearing protectors as measured with two different real-ear attenuation at threshold methods

Despite a high level of sound exposure and a fairly large selection of earplugs available, musicians have often been reported to use personal hearing protectors only seldom. For better hearing conservation, it is important to identify and eliminate the causes for the low motivation to use hearing protection. We explored the usage rate of custom-molded musician's earplugs (ER-15) among 15 symphony orchestra musicians with a questionnaire, and measured the attenuation properties of their earplugs with a Real-Ear Attenuation at Threshold (REAT) procedure in a sound field. Earplug use was found to be low, and the musicians reported that earplugs hampered listening to their own and their colleagues' playing; earplugs affected either timbre or dynamics, or both. Additionally, several reasons related to discomfort of use were itemized, but the musicians who consistently used their earplugs did so in spite of problems with use. The REAT values obtained in sound field were relatively close to the manufacturer's nominal specifications, being 13.7 dB, on average. In the frequency range studied (0.125-8 kHz), individual variation in REAT was, however, up to 15 dB across the measured frequencies. Fluctuation in attenuation might be related to low use of hearing protectors, and REAT measured at fixed center frequencies may be too robust a method to uncover it. We therefore tested 10 additional subjects to find out whether a sweeping signal used in Bιkιsy audiometry would bring more detailed information on earplug attenuation. Mean attenuation was found to be somewhat closer to the nominal attenuation of the ER-9 and ER-15 earplugs up to about 1 kHz, whereas REAT measurements in sound field revealed more even attenuation at frequencies between 1 and 6 kHz. No significant association was found between earplug attenuation properties and earplug use. It was concluded that support and determination to get accustomed to hearing protector use are important factors in hearing conservation.     

Hearing protectors acceptability in noisy environments

OBJECTIVES: Although hearing protectors must be used as a temporary solution, their choice should take into account several aspects, such as ergonomic features, associated with this device. The present study aims to analyse the relationship between the acoustical attenuation efficiency and other aspects related to the comfort afforded by hearing protectors and, consequently, their acceptability when used in industrial noisy environments. METHODS: An evaluation of comfort was performed using a questionnaire, completed by 20 workers. Several scales related to the subjective feeling of comfort were used to quantify the comfort index of a given protector. Simultaneously, the time of usage of each protector was self-recorded by each subject. To test the relationship between the comfort index and the time during which protectors were used, a two-way analysis of variance (two-way ANOVA) was applied. RESULTS AND CONCLUSIONS: The results obtained seem to demonstrate that there are significant differences between catalogued and effective attenuation. Protectors with less catalogued attenuation, but with higher acceptability, i.e. which were more comfortable, tended to be more efficient than protectors with a higher catalogued attenuation, but which were less comfortable. Finally, it must be emphasized that high efficiency can only be achieved through the attainment of an adequate balance between the range of parameters likely to determine its usage.     

Musician earplugs: Appreciation and protection

Recreational music exposure is a potential risk factor for noise-induced hearing loss (NIHL). Augmented hearing protectors have been designed with modified attenuation characteristics to combine hearing protection and listening comfort. However, to date, only a few independent studies have assessed the performance of those augmented protectors in realistic exposure conditions. This study compares the listening experience and temporary effects on cochlear status with different types of earplugs after exposure to contemporary club music. Five different types of commercially available hearing protectors were worn, all commonly used during leisure-time music exposure. Four of them were augmented premolded earplugs and the fifth type was an inexpensive, standard earplug frequently distributed for free at music events. During five different test sessions of 30 min each, participants not professionally involved in music wore one particular type of protector. Contemporary club music was played at sound pressure levels (SPLs) representative of concerts and bars. After each listening session, a questionnaire on sound quality and general appreciation was completed. In addition, otoacoustic emissions (OAEs) were measured directly before and after music exposure. The reported appreciation clearly differed depending on the addressed characteristics and the specific earplug type. In this test group, the reported appreciation mainly depended on comfort and looks, while differences in sound quality were less noticeable. The changes in OAE amplitude before and after noise exposure were small in terms of clinical standards. Nevertheless, the observed temporary shifts differed systematically for the different types of hearing protectors, with two types of musician earplug showing a more systematic decline than the others. Further research with respect to actual use and achieved protection for real, unsupervised music exposure is warranted.     

A trail of individual education for hearing protection with an instrument that measures the noise attenuation effect of wearing earplugs

The aim of this study was to investigate the effect of individual training of workers, using an instrument to quantitatively evaluate the noise attenuation gained with the use of earplugs, on the efforts to promote the use of hearing protection devices. The subjects were 68 male workers exposed to noise of above 80 dBA at an electronic parts manufacturer in Japan. They received group instruction on the prevention of noise-induced hearing loss, and individual education on the effect of the proper use of earplugs. The individual education was done with the use of an instrument that measures the noise attenuation effect of wearing earplugs. After the training, the prevalence of the regular use of hearing protectors increased. Among workers in loud working environments, it increased from 46% to 66% over two months after the training. The percentage of workers who obtained a sufficient noise attenuation effect of>or=25 dB in both ears with the proper use of earplugs also increased, from 46% before the training to 72% immediately afterward. These effects were still observed about two months after the intervention. The results suggest that the present individual training may be an effective means to increase both the usage rate and the proper use of hearing protection devices, perhaps because it deepens individuals' understanding of the effect of the proper use of such devices.     

某市2家机械制造企业噪声接触人员听力防护调查

目的通过了解噪声作业人员个体防护设备的使用及认知情况,找出问题,为今后制定防护对策提供可靠的依据。方法以宜兴市2家噪声危害比较严重的机械制造企业作为调查对象,2011年9月通过问卷和现场调查获得个人防护用品使用情况及噪声防护的认知情况;用国产HS6288B噪声频谱分析仪检测车间噪声;噪声性耳聋由具有诊断资质机构的医师集体依据GBZ 49-2007《职业性噪声聋诊断标准》进行诊断。结果 9个车间中4个车间的噪声超过85 dB(A),最高达92.1 dB(A);听力检查发现有高频听力损失者34人,检出率为14.8%,发现噪声聋患者7人,检出率为3.0%;2个企业的噪声接触人员耳塞佩戴培训率为66.1%,参加噪声危害教育率比较低,为42.2%;全程佩戴耳塞的人员为67.8%,能够完全正确佩戴耳塞的人员仅占18.7%,不戴耳塞的主要原因是与人交流不方便,占48.9%;噪声危害的知晓率为71.7%;正确使用防护用品的知晓率为63.0%。结论企业需要采取综合性的措施提高噪声作业人员耳塞的正确佩戴率,才能达到保护作业人员健康的目的。     

某油田钻井工人噪声接触与个人防护状况调查

目的通过对钻井作业工人防护用品管理和使用情况的调查,为劳动保护措施的实施提供科学依据。方法采用横断面调查方法,对钻井作业环境进行现场调查和噪声监测,并对钻井作业工人进行问卷调查。结果钻井作业工人护耳器(耳塞和耳罩)佩戴率为82.7%;护耳器佩戴率与噪声接触强度有关(P0.01),随噪声强度的增加,护耳器佩戴率有增加的趋势(Z=138.681,P0.01);而与工龄和自觉听力的变化无关(均P0.05);结论钻井作业工人主动防护意识不足,企业应加强教育培训与监督管理,使防护用品得到正确使用。     

Alternative field methods for measuring hearing protector performance

In comparison with the mandatory noise reduction rating (NRR) testing of every hearing protector sold in the United States, real-world tests of hearing protector attenuation are scarce. This study evaluated data from three potential field-test methods as compared with the subject-fit data from Method B of ANSI S12.6-1997 for the E.A.R(R) Express trade mark Pod Plug trade mark. The new field-test methods were the FitCheck headphone (FCH) method, FitCheck in sound field (FCSF) method, and bone-conduction loudness balance (BCLB) method, all of which can be administered in small single-person audiometric booths such as are commonly found in industry. Twenty normal-hearing and audiometrically competent subjects naive to hearing protector use were tested with the laboratory and the three field-test methods in a repeated-measures design. Repeated-measures models with structured covariance matrices were used to analyze the data. Significant effects were found for method, frequency, and first-order frequency-by-gender and frequency-by-method interactions. These effects and interactions were expected given the different psychophysical tasks. The FCSF and BCLB methods provided attenuations that were not significantly different from those found with Method B. Although the attenuations measured for the FCH method were statistically different (greater) than the attenuations from the other methods, the differences were within the magnitude of acceptable test-retest audiometric variability. The results suggest that the FCH and FCSF methods were both feasible and reliable methods for field testing. The FCH method is limited to testing earplugs, and the FCSF requires additional equipment to outfit the test booth, but could be used for testing all types of protectors.     

Field investigations of noise reduction afforded by insert-type hearing protectors

NIOSH conducted field investigations in 1977 and 1981 to determine the actual noise reduction afforded to industrial workers who used insert-type hearing protectors (earplugs) daily. In-situ attenuation tests of 420 workers at 15 industrial plants were conducted to determine the noise reduction provided by earplugs as they were worn during the workday. The workplace results, when compared to manufacturers' best-fit laboratory test results, indicated that 50% of the workers tested were receiving less than one-half the potential attenuation of the earplugs.     

Improvements in sound attenuation performance with earplugs following checklist-based self-practice

The hearing protectors most often used in noisy workplaces are earplugs. The sound attenuation performance of earplugs depends in part on the user's skill and knowledge. This study sought to clarify whether individual training and self-practice based on a checklist can improve sound attenuation. Measurements were performed as follows: Ten subjects, including both men and women, were provided with semi-insert earplugs (E-A-R flex 350-1001) and wore them based only on the printed instructions of the product. Sound attenuation was measured from 125 Hz to 8000 Hz, in accordance with JIS T8161-1983. Intervention was provided through 5 minute individual training with oral and written instructions, followed by 10 minute self-practice each day for 7 days. Sound attenuation was then measured once again. The results indicated significantly improved attenuation, ranging from 7.7 dB to 11.7 dB, in all frequencies following training, confirming the effectiveness of the intervention. This is an easy and effective method for training workers in how to wear earplugs most effectively.     

Variability of real-world hearing protector attenuation measurements

The attenuation provided by a hearing protection device (HPD) in the field is usually estimated by applying a derating factor to the laboratory-determined noise reduction rating (NRR) of the HPD. However, attenuation is highly dependent on individual-specific HPD fit. Prediction of an individual's attenuation depends on the accuracy of the measurement system and the variability of attenuation over time (e.g. after HPD refitting). Variability in attenuation and attenuation test systems has not been adequately characterized to allow for such an assessment. This study compared attenuation measurements made with two systems, Real-Ear-at-Threshold (REAT) and Microphone-in-Real-Ear (MIRE), on 20 workers using two earplugs (foam and custom-molded). Workers' perceptions of the earplugs were also evaluated. Individuals' attenuation results were summarized as personal attenuation ratings (PARs, similar to NRRs). Variability in PARs from between-subject, within-subject and within-day (i.e. repeated tests on a subject without earplug refitting) differences was assessed and used to present the lower confidence limit, or uncertainty factor (UF), of an average individual's attenuation. The custom-molded earplug PARs achieved a higher mean percentage of labeled attenuation than did the foam earplug with both test systems. The custom-molded earplugs also had higher overall acceptance among workers. MIRE PAR levels were lower than REAT levels for both earplugs, but the relationship between the two test systems was highly variable. The MIRE system had lower within-day variability than the REAT system. One individual's MIRE results were highly influential; removal of these results greatly reduced the UF for the custom-molded earplug/MIRE combination. UFs ranged from 8.8 to 13.5 dB. These findings highlight the importance of evaluating variability in individual-specific protection results for personal protective equipment like HPDs, rather than relying on single measurements.     

Relative ear protector performance in high vs low sound levels

The attenuation of one specific ear protector was determined for a group of five normal hearing subjects and a group of five hearing impaired subjects. The hearing impaired group yielded significantly less attentuation than the normal hearing group. Since the measuring sound intensity level was high for the hearing impaired listeners and low for the normal listeners, it appears that a threshold procedure using normal subjects, as presented in the American standard (ANSI S3.19-1974), may overestimate the actual attenuation of ear protectors in most noisy environments.     

Putting the personal back into PPE: hearing protector effectiveness

The lessons learned from this field study of hearing protector attenuation can be distilled for the safety manager into two recommendations: 1) One-on-one training is the best predictor of whether workers will achieve a good fit with their ear plug. While the sheer volume of individual training may appear overwhelming in some facilities, the results were significant and measurable in terms of protecting hearing. 2) If a worker obtains a poor fit with a particular style of ear plug, trying a different pair of ear plugs typically achieves an acceptable attenuation. But even if the different ear plugs do not provide proper fit, the employer still has the option of fitting ear muffs to that worker. Field testing of hearing protectors bridges the gap between the laboratory estimates of attenuation and the real-world attenuation achieved by workers as they normally wear the protectors. But most importantly, it restores the personal back into Personal Protective Equipment. And when it comes to hearing protection, achieving good protection is all personal.     

Evaluation of noise attenuation and verbal communication capabilities using three ear insert hearing protection systems among airport maintenance personnel

The goal of this project was to determine whether one type of earplug would allow a user to hear communication in a noisy environment better than two other types of earplugs. The three types of earplugs studied are newly available on the market. Sonomax SonoCustoms are custom fitted to the user. E-A-R Push-Ins are the newest form of foam earplugs, and Howard Leight SmartFits have an adaptable shape. One of the earplug manufacturers claimed to have improved verbal communications due to the design of the earplug. We hypothesized that the type of earplug providing better communication properties would have lower attenuation around the communication frequencies compared with the other types. To test this hypothesis, we used speech intelligibility and attenuation tests in the laboratory on 26 subjects, and real-time video exposure monitoring in the field (airport maintenance personnel) for visual communication cues. ANCOVA was used to analyze the data from the laboratory study. The type of earplug worn was not significant in the model (p-value 0.0849), nor was attenuation of the earplug (p-value 0.2379). Further analysis showed that attenuation did not differ significantly among earplugs (p-value 0.5903). Logistic regression was used to analyze the data from the field study. Again, the type of earplug was not significant in the model (p-value 0.0965). A comfort questionnaire determined that Howard Leight SmartFits and the E-A-R Push-Ins were more comfortable and easier to use than the Sonomax HPDs (p-value <0.0001). We found a definite difference between manufacturers' attenuation data and our attenuation data, especially in the frequencies for 125-1000 Hz. Also, there was no difference in frequency and overall attenuation among the HPDs. This resulted in no difference in communication abilities among the types of HPDs.     

The effects of protector-noise interaction on the accuracy of the NRR estimate of hearing protector attenuation

A total of 262 noise spectra were divided empirically into three groups and the accuracy of the NRR estimate of hearing protector attenuation was evaluated for each group using 15 hearing protectors. The mean and the standard deviation of the error in the NRR estimate was most stable across the 15 protectors, when noise spectra were characterized by a simple monotonic band-level function yielding a dBC-dBA difference of 3.5 dB or less. Both the octave band attenuation function of the hearing protector and the octave band spectrum of the noise appeared to contribute to the error in the NRR estimate.     

Individual fit-testing of earplugs: a review of uses

Individual fit-testing of earplugs is an exciting new trend in hearing conservation. This article reviews how this technology is being used to protect noise-exposed workers. Earplug fit-testing systems are becoming more commercially available and more feasible for field use. Individual fit-testing is no longer used only for research investigations but is being incorporated in Hearing Conservation Programs (HCP) to improve training, document protection and evaluate the effectiveness of the hearing protector element of an effective HCP.     

The challenge of localizing vehicle backup alarms: effects of passive and electronic hearing protectors, ambient noise level, and backup alarm spectral content

A human factors experiment employed a hemi-anechoic sound field in which listeners were required to localize a vehicular backup alarm warning signal (both a standard and a frequency-augmented alarm) in 360-degrees azimuth in pink noise of 60 dBA and 90 dBA. Measures of localization performance included: (1) percentage correct localization, (2) percentage of right--left localization errors, (3) percentage of front-rear localization errors, and (4) localization absolute deviation in degrees from the alarm's actual location. In summary, the data demonstrated that, with some exceptions, normal hearing listeners' ability to localize the backup alarm in 360-degrees azimuth did not improve when wearing augmented hearing protectors (including dichotic sound transmission earmuffs, flat attenuation earplugs, and level-dependent earplugs) as compared to when wearing conventional passive earmuffs or earplugs of the foam or flanged types. Exceptions were that in the 90 dBA pink noise, the flat attenuation earplug yielded significantly better accuracy than the polyurethane foam earplug and both the dichotic and the custom-made diotic electronic sound transmission earmuffs. However, the flat attenuation earplug showed no benefit over the standard pre-molded earplug, the arc earplug, and the passive earmuff. Confusions of front-rear alarm directions were most significant in the 90 dBA noise condition, wherein two types of triple-flanged earplugs exhibited significantly fewer front-rear confusions than either of the electronic muffs. On all measures, the diotic sound transmission earmuff resulted in the poorest localization of any of the protectors due to the fact that its single-microphone design did not enable interaural cues to be heard. Localization was consistently more degraded in the 90 dBA pink noise as compared with the relatively quiet condition of the 60 dBA pink noise. A frequency-augmented backup alarm, which incorporated 400 Hz and 4000 Hz components to exploit the benefits of interaural phase and intensity cues respectively, slightly but significantly improved localization compared with the standard, more narrow-bandwidth backup alarm, and these results have implications for the updating of backup alarm standards.     

应用插入传声器法测量护耳器在高强脉冲噪声作用下的声衰减

该研究的目的是应用插入传声器研究一种护耳器声衰减现场人体客观测试法。插入传声器上装有一个外径为1.5毫米的有机树指软管用以将耳道的声压传递给耳道外部的传声器。经实验室实验和处理得出一个公式以修正软管本身带来的影响。实验结果表明插入传声器法所测护耳器声衰减结果和传统的主观法所测结果在低于3.15KHz频段内是一致的。并克服了主观法低频段生理噪声误差.因此插入传声器法是一可靠的人体客观测试方法。现场测试还表明泡沫塑料耳塞(E.A.R)的声衰减与大容积耳罩一样。耳塞、耳罩同时佩戴声衰减效果有大幅度提高(提高6-18dB)。     

Subjective evaluation of a prototype earmuff exhibiting flat and nonlinear attenuation characteristics

Subjective user responses were obtained for a test earmuff exhibiting approximately flat (uniform) attenuation of about 25 dB from 500 to 8000 Hz for sound pressure levels (SPLs) less than 120 dB. At SPLs above 120 dB, the test earmuff exhibited nonlinear (level-dependent) attenuation characteristics such that noise reduction increased with increasing sound level. The study population consisted of police officers from the Raleigh, North Carolina, Police Department as they were performing arms requalification by executing a series of firing programs during two sequential and identical relays. The study subjects wore either the test earmuff or a comparable conventional earmuff during the first relay, then the alternate protector for the second relay with the order counterbalanced. Results indicated a significant preference for the test earmuff in three comparison areas: comfort, perceived hearing protection, and speech understanding. The study demonstrates that ammunition type and level of noise exposure contributed significantly to a preference in favor of the test earmuff. The subjects who used the quietest of the ammunition types rated the test earmuff significantly better than the remaining subjects with respect to speech understanding.     

某煤矿接噪工人使用降噪耳塞效果分析

目的观察降噪耳塞对煤矿接噪工人噪声性听力损失的预防效果。方法以208名（416耳）佩戴3M1110子弹型带线耳塞3年的煤矿接噪工人为耳塞组,分析其3年前后纯音听阈测定结果,并与未佩戴耳塞的同单位接噪工人对照组进行比较。结果用SPSS18软件分析。结果耳塞组与对照组比较,佩戴耳塞前,两组听力差异无统计学意义（P〉0．05）;佩戴耳塞3年后,两组听力差异有统计学意义（P〈0．05）。耳塞组佩戴降噪耳塞3年前后听力减退差异无统计学意义（P〉0．05）。结论降噪耳塞对保护煤矿接噪工人的听力,防止噪声性听力损失具有一定作用。