Effects Of Hearing Protection Devices Research Articles

Evaluation of hearing protection device effectiveness for musicians

Objective To evaluate musicians’ personal attenuation and perceptions of three types of hearing protection devices (HPDs): formable foam earplugs and both non-custom and custom versions of uniform attenuation earplugs (UAEs) marketed to musicians. Design A mixed-methods approach was used to evaluate the HPDs. Audiometric testing obtained hearing levels at baseline and with each HPD across frequencies (125–8000 Hz) to determine personal attenuation ratings and uniformity of attenuation. Participants completed surveys over six months regarding how often they used the HPDs and their perceptions about wearing them. Study sample Twenty-four musicians were recruited to participate. Results Substantial variability was observed in the attenuation achieved among participants for each HPD type, but custom UAEs provided the most consistent attenuation across frequencies. Participants’ HPD preferences were influenced by multiple factors including personal instrument and specific activity. Custom UAEs were most frequently used but usage rates continually decreased over the 6-month period. Conclusions Fit-testing is important to determine fit and sizing. Combining information on the effectiveness of HPDs with musicians’ opinions about wearing them can inform recommendations for which types may be the most effective and feasible options for reducing sound exposures.

The Effectiveness of Hearing Protection Devices: A Systematic Review and Meta-Analysis.

To prevent intensive noise exposure in advance and be safely controlled during such exposure, hearing protection devices (HPDs) have been widely used by workers. The present study evaluates the effectiveness of these HPDs, partitioned into three different outcomes, such as sound attenuation, sound localization, and speech perception. Seven electronic journal databases were used to search for published articles from 2000 to 2021. Based on inclusion criteria, 20 articles were chosen and then analyzed. For a systematic review and meta-analysis, standardized mean differences (SMDs) and effect size were calculated using a random-effect model. The funnel plot and Egger’s regression analysis were conducted to assess the risk of bias. From the overall results of the included 20 articles, we found that the HPD function performed significantly well for their users (SMDs: 0.457, 95% confidence interval (CI): 0.034–0.881, p < 0.05). Specifically, a subgroup analysis showed a meaningful difference in sound attenuation (SMDs: 1.080, 95% CI: 0.167–1.993, p < 0.05) when to wear and not to wear HPDs, but indicated no significance between the groups for sound localization (SMDs: 0.177, 95% CI: 0.540–0.894, p = 0.628) and speech perception (SMDs: 0.366, 95% CI: −0.100–1.086, p = 0.103). The HPDs work well for their originally designated purposes without interfering to find the location of the sound sources and for talking between the workers. Taking into account various factors, such as the characteristics of the users, selection of appropriate types, and fitting methods for wearing in different circumstances, seems to be necessary for a reliable systematic analysis in terms of offering the most useful information to the workers.

Effect of Hearing and Head Protection on the Localization of Tonal and Broadband Reverse Alarms.

ObjectiveThis study explored the effects of hearing protection devices (HPDs) and head protection on the ability of normal-hearing individuals to localize reverse alarms in background noise.BackgroundAmong factors potentially contributing to accidents involving heavy vehicles, reverse alarms can be difficult to localize in space, leading to errors in identifying the source of danger. Previous studies have shown that traditional tonal alarms are more difficult to localize than broadband alarms. In addition, HPDs and safety helmets may further impair localization.MethodStanding in the middle of an array of eight loudspeakers, participants with and without HPDs (passive and level-dependent) had to identify the loudspeaker emitting a single cycle of the alarm while performing a task on a tablet computer.ResultsThe broadband alarm was easier to localize than the tonal alarm. Passive HPDs had a significant impact on sound localization (earmuffs generally more so than earplugs), particularly double hearing protection, and level-dependent HPDs did not fully restore sound localization abilities. The safety helmet had a much lesser impact on performance than HPDs.ConclusionWhere good sound localization abilities are essential in noisy workplaces, the broadband alarm should be used, double hearing protection should be avoided, and earplug-style passive or level-dependent devices may be a better choice than earmuff-style devices. Construction safety helmets, however, seem to have only a minimal effect on sound localization.ApplicationResults of this study will help stakeholders make decisions that are more informed in promoting safer workplaces.

The Effect of Hearing-Protection Devices on Auditory Situational Awareness and Listening Effort.

Hearing-protection devices (HPDs) are made available, and often are required, for industrial use as well as military training exercises and operational duties. However, these devices often are disliked, and consequently not worn, in part because they compromise situational awareness through reduced sound detection and localization performance as well as degraded speech intelligibility. In this study, we carried out a series of tests, involving normal-hearing subjects and multiple background-noise conditions, designed to evaluate the performance of four HPDs in terms of their modifications of auditory-detection thresholds, sound-localization accuracy, and speech intelligibility. In addition, we assessed their impact on listening effort to understand how the additional effort required to perceive and process auditory signals while wearing an HPD reduces available cognitive resources for other tasks. Thirteen normal-hearing subjects participated in a protocol, which included auditory tasks designed to measure detection and localization performance, speech intelligibility, and cognitive load. Each participant repeated the battery of tests with unoccluded ears and four hearing protectors, two active (electronic) and two passive. The tasks were performed both in quiet and in background noise. Our findings indicate that, in variable degrees, all of the tested HPDs induce performance degradation on most of the conducted tasks as compared to the open ear. Of particular note in this study is the finding of increased cognitive load or listening effort, as measured by visual reaction time, for some hearing protectors during a dual-task, which added working-memory demands to the speech-intelligibility task. These results indicate that situational awareness can vary greatly across the spectrum of HPDs, and that listening effort is another aspect of performance that should be considered in future studies. The increased listening effort induced by hearing protectors may lead to earlier cognitive fatigue in noisy environments. Further study is required to characterize how auditory performance is limited by the combination of hearing impairment and the use of HPDs, and how the effects of such limitations can be linked to safe and effective use of hearing protection to maximize job performance.

Occlusion effects of hearing protection device on ear canal transfer function and cochlear injury from impulse noise exposure

The objective of this paper is to present a new finding on the effects of hearing protection devices (HPDs) on the ear canal (EC) transfer function (TFEC2ED). Specifically, we show that when an earmuff is worn, the TFEC2ED is not the same as that for the bare head, leading to a significant difference in cochlear injury prediction. We used shock tube blast with an acoustical test fixture (ATF) fitted with the recovered earmuffs from the historic blast overpressure project (BOP) to measure the TFEC2ED. A microphone was placed at the EC entrance under the earmuff (undermuff) to measure the pressure at the EC entrance, while the built-in ATF’s microphone was used to measure the eardrum (ED) pressure. The TFEC2ED is defined as the ratio of the pressure at the ED to the pressure at the EC entrance. We compared the cochlear integrated energy (ICE) values, when the TFEC2ED obtained from bare head (Case-1) and that measured using the ATF fitted with an earmuff (Case-2), respectively are used in the ICE-model, to estimate the effects of the difference between the TFEC2EDs on injury. The human BOP undermuff pressure data were used as model input. For Case-1, the input was at the EC. The ED pressure, reconstructed using the undermuff pressure and the TFEC2ED measured using the ATF, was used for Case-2. We found significant differences in the ICE-values as the result of the difference between the TFEC2EDs. We conclude that hearing protector models must correctly model the occlusion effects of HPDs by incorporating the change in the TFEC2ED.

Acute Acoustic Trauma among Soldiers during an Intense Combat.

During military actions, soldiers are constantly exposed to various forms of potentially harmful noises. Acute acoustic trauma (AAT) results from an impact, unexpected intense noise ≥140 dB, which generates a high-energy sound wave that can damage the auditory system. We sought to characterize AAT injuries among military personnel during operation "Protective Edge," to analyze the effectiveness of hearing protection devices (HPDs), and to evaluate the benefit of steroid treatment in early-diagnosed AAT injury. We retrospectively identified affected individuals who presented to military medical facilities with solitary or combined AAT injuries within 4 mo following an intense military operation, which was characterized with an abrupt, intensive noise exposure (July-December 2014). A total of 186 participants who were referred during and shortly after a military operation with suspected AAT injury. HPDs, oral steroids. Data extracted from charts and audiograms included demographics, AAT severity, worn HPDs, first and last audiograms and treatment (if given). The Student's independent samples t test was used to compare continuous variables. All tests were considered significant if p values were ≤0.05. A total of 186 participants presented with hearing complaints attributed to AAT: 122, 39, and 25 were in duty service, career personnel, and reservists, with a mean age of 21.1, 29.2, and 30.4 yr, respectively. Of them, 92 (49%) participants had confirmed hearing loss in at least one ear. Hearing impairment was significantly more common in unprotected participants, when compared with protected participants: 62% (74/119) versus 45% (30/67), p < 0.05. Tinnitus was more common in unprotected participants when compared with protected participants (75% versus 49%, p = 0.04), whereas vertigo was an uncommon symptom (5% versus 2.5%, respectively, p > 0.05). In the 21 participants who received steroid treatment for early-diagnosed AAT, bone-conduction hearing thresholds significantly improved in the posttreatment audiograms, when compared with untreated participants (p < 0.01, for 1-4 kHz). AAT is a common military injury, and should be diagnosed early to minimize associated morbidity. HPDs were proven to be effective in preventing and minimizing AAT hearing sequelae. Steroid treatment was effective in AAT injury, if initiated within 7 days after noise exposure.

Evaluation of noise exposures and hearing loss at a hammer forge company

The NIOSH health hazard evaluation program evaluated employees’ exposures to high level continuous and impact noise at a hammer forge company. Personal dosimetry data were collected from 38 employees and noise exposure recordings were collected during two visits to the facility. Extensive audiometric records were reviewed and trends for hearing loss, threshold shifts and risk of hearing loss were assessed. The effectiveness of hearing protection devices for hammer forging was evaluated with an acoustic test fixture. A longitudinal analysis was conducted on the audiometric data set that included 4750 audiograms for 483 employees for the years 1981 to 2006. The analysis of the audiometric history for the employees showed that 82% had experienced a NIOSH-defined hearing threshold shift and 63% had experienced an OSHA-defined standard threshold shift. The mean number of years from a normal baseline audiogram to a threshold shift was about 5 years for a NIOSH threshold shift and was about 9 years for an OSHA t...

Predicting sound-localization performance with hearing-protection devices using computational auditory models

Evaluation of the effect of hearing-protection devices (HPDs) on auditory tasks such as detection, localization, and speech intelligibility typically is done with human-subject testing. However, such data collections can be impractical due to the time-consuming processes of subject recruitment and the testing itself, particularly when multiple tasks and HPDs are included. An alternative, objective testing protocol involves the use of a binaural mannequin (a.k.a an acoustic test fixture) and computational models of the auditory system. For example, data collected at the eardrums of such a mannequin outfitted with an HPD can be fed into a binaural localization model. If the performance of the model with such input can be shown to be similar to that of human subjects, the model-based assessment may be sufficient to characterize the hearing protector and inform further design decisions. In this presentation we will describe the preliminary results of an effort to replicate human-subject localization performan...

An objective, efficient auditory situation awareness test battery for advanced hearing protectors and tactical communications and protective systems (TCAPS): DRILCOM (detection-recognition/identification-localization-communication)

An objective, computer-controlled test battery was developed for measuring the effects of hearing protection devices (HPDs) and TCAPS, on auditory situational awareness (ASA). Four independent ASA tasks with military relevance were tested: Detection-Recognition/Identification-Localization-Communication (DRILCOM). Detection employed threshold-shift with seven 1/3-octave bands, an AK-47 burst, and rifle cocking. Detection signals emanated from in front of the subject (0 degrees), or at 90, 180, or 270 degrees, to evaluate directionality. The Recognition/Identification task employed 36 signals combined in triads, wherein one “target” sound from 0 or 90 degrees had to be identified, at S/N ratios of -10, 0, and + 10. Localization employed a dissonant pure tone chord, spanning 104-7880 Hz, which provided interaural time and interaural level cuing. Localization entailed 360-degrees of azimuth in 30-degree increments, and 30-degrees in frontal elevation, at a S/N of + 10. The Communications task, addressing pass-through communications, utilized QuickSIN messages from 4 directions. In a proof-of-concept experiment on 10 subjects, 2 in-ear TCAPS, 1 earmuff TCAPS, a passive Combat Arms Earplug in “open” setting, and an EB-15LE™ electronic earplug were tested, as well as the open ear. DRILCOM demonstrated sensitivity to performance differences among devices and the open ear, as well as diagnosticity to within-device performance differences across different ASA tasks. The results have implication for selection and deployment of TCAPS and HPDs.

260 Interventions to prevent occupational noise-induced hearing loss - a Cochrane Review

ObjectivesMillions of workers worldwide are exposed to noise levels that increase their risk of hearing impairment. Little is known about the effectiveness of hearing loss prevention interventions. Therefore we assessed...

Measurement of Hearing Protection Devices Performance in the Workplace during Full-Shift Working Operations

The effectiveness of hearing protection devices (HPDs), when used in workplace conditions, has been shown over the years to be usually lower than the labeled values obtained under well-controlled laboratory conditions. Causes for such discrepancies have been listed and discussed by many authors. This study is an attempt to understand the issues in greater details and quantify some of these factors by looking at the performance of hearing protectors as a function of time during full work shift conditions. A non-invasive field microphone in the real ear (F-MIRE)-based method has been developed for measuring the effectiveness of different HPDs as a function of time in the workplace. Details of the test procedures, the equipment used, and the post-processing operations are presented and discussed. The methodology was developed in such a way that a complete time and frequency representation are possible. The system was used on a total of 24 workers in eight different companies. Work shifts of up to 9-h long were recorded. Various types of earmuffs and one type of molded earplugs were tested. Attenuation data reported as a function of time showed, for most workers tested, considerable fluctuations over entire work shift periods. Parts of these fluctuations are attributed to variations in the low-frequency content in the noise (in particular for earmuffs) as well as poor insertion and/or fitting of earplugs. Lower performances than laboratory-based ones were once again observed for most cases tested but also, important left and right ear differences were obtained for many individuals. When reported as a function of frequency, the attenuation results suggested that the few approximations used to relate the measurements to subjective real-ear-attenuation-at-threshold (REAT) data were realistic. The use of individualized attenuation data and performance ratings for HPDs as well as a good knowledge of the ambient noise in the workplace are key ingredients when evaluating the performance of hearing protectors in field conditions.

Use and protection effects of hearing protection devices

目的 探索不同噪声环境下现场使用几种护耳器(hearing protection devices,HPD)的实际防护效果.方法 182名基础听力正常的接触噪声人员分别使用不同的HPD,其中接触噪声强度为85.1～89.3 dB(A)的调查对象分别使用硅橡胶耳塞(58人)和慢回弹耳塞(57人),接触噪声强度为93.6～104.1 dB(A)者使用耳罩(31人),接触噪声强度为92.4～104.3 dB(A)者使用复合HPD(耳塞+耳罩)(36人).对各组调查对象连续进行3年纯音听力监测,测试0.5～6.0 kHz6个频率的听阈值,比较3年间听力损失检出率和听阈偏移阳性率的差异.结果 各组连续3年轻度高频听力损失检出率分别为硅橡胶耳塞组0、1.79%、5.67%.慢回弹耳塞组0、1.85%、3.85%,耳罩组0、10.34%、27.59%,复合HPD组0、2.86%、8.82%,2个耳塞组之间听力损失检出率的差异无统计学意义(P>0.05).但耳罩组第3年轻度高频听力损失检出率明显高于复合HPD组,差异有统计学意义(P 0.05).结论 HPD对接触噪声人群的听力有明显的保护作用,复合HPD能提供更有效的保护.HPD的使用可有效地遏制噪声性听力损失随接触年限的延长而增加的趋势。

Investigation of hearing protection effects in an extreme noise environment with an alarm location problem

The purpose of this study is to determine optimum locations of alarm devices and the effects of hearing protection in an extremely noisy environment. A machining facility has been selected as a working environment because it usually generates extremely high noise level. First, an analytical model is presented for predicting the optimal number of alarm devices, their locations, and their sound intensities if equipment operators have no hearing protection (Case 1). LINGO ®, optimization software of LINDO Systems Inc., is used for an analytical tool in this study. Second, the optimal solutions are evaluated for their feasibility in the following two cases: the first case in which some operators have hearing protection at or above 90 dBA (Case 2) and the other case in which all operators have hearing protection regardless of noise levels (Case 3). Tukey–Kramer tests of the three cases are conducted to find if the significant effects of hearing protection devices exist. The results support the maximum permissible noise level of 85 dBA. Thus, Occupational Safety and Health Administration (OSHA) standard of hearing protection should be stricter because hearing loss may be expected due to high alarm sound by a masking effect of background noise in extremely noisy manufacturing facilities. Relevance to industry The study provides facility planners and safety engineers with a model that may assist in positioning alarms in a noisy environment. The results may help to support the national standard of hearing protection use. In addition, the results may provide guidelines to solve other alarm location problems relating to the intensity of sound.

Optimizing Alarm Location and Effects of Hearing Protection for Machining Industries

Emergency alarm systems are extremely important in our daily life since these can provide adequate and timely warning to people in event of threatened disaster. These systems cause a traumatic hearing loss due to their extremely high sound level. Hearing protection devices are the most popular and convenient solution for avoiding a traumatic hearing loss. However, the study of alarm location problems with hearing protection has not been much paid attention. The purposes of this study were; (1) to determine the number of alarm devices, their optimum locations and minimum sound power levels and; (2) to find the effectiveness of hearing protection devices. The selected working environment was a machining facility that usually generates extremely high noise level. An analytical model was provided and the effects of hearing protection devices were discussed with two examples. The results showed that hearing protection was highly required at or above 85dBA noisy environment.

The Impact of Hearing Protection on Sound Localization and Orienting Behavior

The effect of hearing protection devices (HPDs) on sound localization was examined in the context of an auditory-cued visual search task. Participants were required to locate and identify a visual target in a field of 5, 20, or 50 visual distractors randomly distributed on the interior surface of a sphere. Four HPD conditions were examined: earplugs, earmuffs, both earplugs and earmuffs simultaneously (double hearing protection), and no hearing protection. In addition, there was a control condition in which no auditory cue was provided. A repeated measures analysis of variance revealed significant main effects of HPD for both search time and head motion data (p < .05), indicating that the degree to which localization is disrupted by HPDs varies with the type of device worn. When both earplugs and earmuffs are worn simultaneously, search times and head motion are more similar to those found when no auditory cue is provided than when either earplugs or earmuffs alone are worn, suggesting that sound localization cues are so severely disrupted by double hearing protection the listener can recover little or no information regarding the direction of sound source origin. Potential applications of this research include high-noise military, aerospace, and industrial settings in which HPDs are necessary but wearing double protection may compromise safety and/or performance.

Effectiveness of Hearing Protection Devices in the Hazard Reduction of Noise from Used Tractors

Old and worn agricultural tractors show typically high noise levels, due to the natural deterioration of the engine, the gearbox and other components of the machine (tyres, exhaust). Despite the limit of technical obsolescence of tractors being commonly fixed at 10 yr, a large number of older machines are still in use in Italy.The noise produced by 60 used old tractors, working in farms located in Northern Italy, was recorded with the aim of ascertaining to what extent the use of the hearing protection devices (HPD) could significantly reduce the noise perceived by the driver. The performance, in terms of noise reduction rating and single number rating of 40 earmuffs, 54 earplugs and 27 ear canal caps was examined. For every tractor, the use of all 121 HPDs was simulated, to determine both the best and the worst conditions.Considering the Occupational Safety Health Administration and National Institute for Occupational Safety and Health recommendations for decreasing the laboratory noise reduction ratings (to take into account the “real-world” attenuation), it can be concluded that, on average, 10 dB(A) of attenuation can be achieved.As the average noise level found at the tractor driver's ear was about 87–88 dB(A), with a maximum of 101 dB(A), this means that using the HPDs the noise could be reduced to 77–78 dB(A), up to 90–91 dB(A). This may be considered a fairly good result, but it should be recognized that the effectiveness of HPDs may vary widely from worker to worker, depending on correct wearing and wearing time.

Unusual jobs require unusual methods for noise exposure measurement

With the diversity of the American workplace, the one size fits all approach cannot accommodate every occupational noise exposure measurement challenge. This is precisely why ANSI Standard S12.19-1996, ‘‘Measurement of Occupational Noise Exposure,’’ permits different measurement criteria and a variety of instrumentation and methodologies. The Occupational Safety and Health Administration (OSHA) and the Mine Safety and Health Administration (MSHA) use employee-worn noise dosimeters almost exclusively to document alleged violations of the occupational noise standards. However, employers and consultants may use any method that properly identifies those employees who need to be included in a hearing conservation program and that relates the noise exposure with the risk of occupational hearing loss and the effectiveness of hearing protection devices. Some environmental and operational hearing loss and the effectiveness of hearing protection devices. Some environmental and operational problems that affect occupational noise measurement are temperature, humidity, rain, wind, radio, magnetic and microwave interference, intrinsic safety, and the presence of hazardous materials. To illustrate effective handling of these measurement problems, the methodologies used in the occupational noise exposure assessment of operating municipal departments will be discussed.

DETECTION OF WARBLE TONES IN WIDEBAND NOISE WITH AND WITHOUT HEARING PROTECTION DEVICES

Noise attenuation by linear hearing protection devices (HPDs) is considered to be independent of the environmental noise level. Linearity of HPDs is one of the basic assumptions underlying the Real Ear Attenuation at the Threshold (REAT) method of HPD testing, which utilizes quiet conditions. However, non-linear growth of masking at high intensity levels may result in the effects of HPDs on detection of speech and warning signals being different from those at high noise levels. The purpose of this study was to determine if the non-linear growth of masking can affect detection of warble signals by persons using HPDs in wideband noise presented at the 100 dB(A) level. Audiometric thresholds of hearing of 10 listeners were measured under four experimental conditions: (1) noise off, HPDs off (condition C1); (2) noise off, HPDs on (condition C2); (3) noise on, HPDs on (condition C3); and (4) noise on, HPDs off (condition C4). The results of this study indicate that detection of signals by persons using HPDs in noise < 100 dB(A) can be well predicted from noise attenuation characteristics of HPDs measured in quiet without the need for a correction factor accommodating non-linear growth of masking. This finding has implications for predicting the audibility of warning signals in noise by persons wearing HPDs.

Noise and hearing conservation: Young adults’ habits, knowledge, and attitudes.

According to the National Institutes of Health (NIH), approximately 28 million individuals in the United States suffer from significant hearing loss. More than one-third of those losses are attributable to noise exposure [Lankford, Hearing Instruments 41(10), 6 (1990)]. Between 1971 and 1985, the number of persons aged 35–44 years suffering from hearing loss increased from approximately 55 to 85 per thousand−a larger increase than for the 45–54 or 65 year old and older age group. Two hundred young adults, ages 14 to 38 years, were surveyed via a 20-item questionnaire concerning their habits pertaining to, knowledge of, and attitudes toward noise and hearing conservation. Results indicated that the majority of young adults participated in activities exposing them to excessive noise levels at least twice a week and for several hours in duration for each activity. Further, the large majority reported at least one incident of having symptoms (e.g., tinnitus) of overexposure to noise resulting from those activities. Although the large majority demonstrated basic knowledge about the effects of noise on hearing, most had deficiencies in their knowledge of the effectiveness of hearing protection devices (HPDs) and would feel self-conscious in using them or taking other measures to circumvent noise-induced hearing loss.

Limitations of hearing protection devices (HPDs) as used in real-world environments

The effectiveness of hearing protection devices (HPDs) and problems associated with HPD usage have been investigated to-date at over 100 plant sites covering a seven state area. The primary objectives of the study are to identify HPD usage related problems and to develop solutions for the problems defined. The findings have not identified any consistent significant problems. The most common types of problems identified, in order of descending importance, were: discomfort, HPD design limitations, canal irritation, infection, and problems related to HPD fitting, storage and maintenance. In addition, the effectiveness of HPDs in preventing on-the-job temporary threshold shifts has been established to be significantly less than would be predicted using laboratory generated attenuation data. Based on these findings it is concluded that the identified HPD usage related problems can be handled by implementing effective educational programs and administrative procedures.