Hearing Protection Research Articles

Custom hearing protection devices: Are they better?

When hazardous noise is unavoidable, hearing protection devices (HPDs) are used to reduce the risk of noise-induced hearing injuries. The question of which HPD is appropriate or “the best” is often a subject of debate. Appropriateness may be dictated by environmental factors, such as noise exposure type and level, mission requirements such as communication needs, compatibility with other personal protective equipment, or even personal preference. Regardless of the type used, properly fitting hearing protection is paramount to prevent or reduce hazardous noise entering the auditory system. Custom HPDs are designed to fit the specific anatomy of an individual and, when made and fit properly, may be appropriate for many applications and missions (e.g., band members, certain aviators). In addition to being tailor-made to each individual, custom HPDs may be designed to couple with communication devices, frequency or level-specific filters, and/or may incorporate electronics to provide capabilities such as amplification or reduction of ambient noise. Attenuation performance of custom HPDs coupled to a communication earplug (CEP) was measured and compared to traditional foam HPDs coupled to the CEP. This discussion will include custom HPD fabrication options, performance characteristics, benefits, drawbacks, and finally their potential real-world application.

Enhancing hearing protection in complex noise environments with extended-wear hearing aids

Conventional hearing protection devices (HPDs) work well in predictable noise environments where it is practical to put them on prior to exposure and remove them after. However, some noise environments are characterized by long periods of relative quiet that are unpredictably interrupted by brief periods of hazardous noise. These environments make it difficult to ensure that HPDs are worn when exposure to hazardous levels occurs. One possible solution is the extended-wear hearing aid (EWHA), a hearing aid that completely blocks the ear canal and can remain in the ear for months at a time. Previous research has shown that the EWHA can provide protection from impulse noise without significantly interfering with detection and localization of environmental sounds. At that time, the major drawback of the EWHA was that once it was removed it could only be re-inserted by an audiologist. This limitation has been addressed by the development of a self-insertion tool that allows users to remove and re-insert the EWHA as desired. We will discuss the potential advantages of using the EWHA as an HPD, with an emphasis on situations where the EWHA could be used to reduce noise exposure without modifying the current commercially available device.

A new method for measurement of impulsive peak level attenuation of hearing protectors

ASA/ANSI S12.42-2010 contains the first standardized test method for measuring the performance of hearing protection devices (HPDs) with high-level impulsive noise. This standard defines the impulsive peak insertion loss (IPIL) as a time-domain metric that quantifies the reduction in peak sound pressure level provided by an HPD for impulsive noises. However, IPIL as defined in S12.42-2010 is dependent on the spectrum of the impulsive noise source used for measurements of HPDs. Recent studies of HPDs with impulsive noise have led to the investigation of frequency-domain metrics and calculation methods. Using frequency-domain calculations allows the impulsive peak level attenuation to be computed for a wide range of impulsive noises, not only those used for the measurement. Consequently, significant revisions to S12.42 are under consideration and a new standard, ISO 4869-7, is being developed in parallel with the ANSI revision. This presentation highlights key proposals and substantive changes including: measurement and calculation of the frequency-dependent impulsive insertion loss (IIL), incorporation of frequency-domain aspects such as real-ear attenuation at threshold (REAT) limits to attenuation, and a new impulsive peak level attenuation metric (IPLA) to be calculated from the REAT-bounded IIL.

Measuring the effect of electronic hearing protection devices on behavioral detection thresholds

Electronic hearing protection devices can provide amplification for quiet ambient sounds, while still providing protection against loud sounds. These can be important in environments with sporadic and unpredictable hazardous noise, but also with a need for maintaining awareness of ambient sounds, or for conducting face-to-face communication. This study’s aim was to understand what impact electronic hearing protection devices have on auditory detection thresholds. Human subjects were used to measure thresholds for narrowband noise bursts without hearing protection, with electronic hearing protectors powered off, and with electronic hearing protectors powered on with several gain settings. In addition, electroacoustic measurements were made of the input/output functions and electronic noise floors of the hearing protectors at the same gain settings. The data showed that thresholds in quiet with electronic hearing protectors were higher than without, regardless of the device amplification. This could be attributed to the hearing protector electronic noise limiting performance. Thresholds measured with ambient masking noise were similar across open ear and device conditions, reflecting that the signal-to-noise ratio for ambient sounds does not change with amplification. Listeners with a simulated conductive hearing loss had lower thresholds with an electronic hearing protector than without, suggesting a benefit of the device amplification.

Method to measure the effect of acoustic leaks on active noise reduction device performance

Passive hearing protection (HP) systems are designed to reduce the level of noise at the ear. Passive HP typically excel in attenuating mid- to high-frequency noise. Active noise reduction (ANR) has the potential to provide additional attenuation of low-frequency noise. There are documented reports describing unwanted sound being generated by ANR systems if an acoustic leak is present. The objective of this effort was to develop a method to measure the performance of ANR devices with and without the introduction of an acoustic leak. A number of ANR earcups were selected for this study. Data were collected with an artificial ear and a flat base plate in a noise environment that ranged from 65–115 dB SPL. Wedges, designed in-house, created a consistent acoustic leak that ranged in size from 1–2 mm in radius. The results revealed that some ANR earcups provided high levels of protection when the earcup was well-sealed; however, when an acoustic leak was introduced, the earcups became unstable and generated noise in the earcup. This instability was not seen in all ANR devices. The outcome of these measurements solidified the need for a method to measure ANR device performance when acoustic leaks are introduced.

High level sound transmission through cadaver human ears—On the influence of bone conduction and hearing protective devices

High level sound exposure can cause substantial injury to the auditory system, motivating efforts to predict and prevent this injury. Measurement techniques using acoustic manikins are effective for low and moderate sound levels, but nonlinear effects in the middle ear and alternate sound transmission pathways to the inner ear limit their utility at higher sound pressure levels. Here, we describe results from a series of measurements made in cadaveric human ears conducted in our laboratory over the last several years. We quantified sound transmission to the inner ear by measuring the difference in sound pressure level across the cochlear partition near the base of the cochlea, which drives basilar membrane motion. We describe measurements quantifying sound transmission through the human middle ear, which is limited by suspensory ligaments for sounds above approximately 130 dB SPL, resulting in nonlinear (harmonic) distortion of sounds in the cochlea at higher sound pressure levels. Similarly, we describe observations of sound transmission to the cochlea via bone conduction from vibratory transducers, as well as high level sound and impulse noise/blast exposures. The implications of these measurements for hearing loss predictions, effectiveness of hearing protective devices, and injury mechanisms are discussed.

Protecting beyond the bone-conduction limit: Lessons learned developing and fielding a passive Hearing Protection Helmet

Traditional hearing protection devices focus on attenuating air-conducted sound and are limited by the bone conduction threshold (Berger, 1983). In extreme noise fields, such as aircraft maintainers operating near jet engines on aircraft carriers, the bone conducted pathway carries sufficient energy to damage the cochlea. Here, we describe the development, qualification, and field-testing of a passive Hearing Protection Helmet (HPH) designed to surpass the bone conduction limit. The HPH features a noise-isolating shell sealed to the head via a compliant edge seal. When worn with foam earplugs and tested to ANSI S12.6-2016 (Experimenter Fit), the Noise Reduction Rating (NRR) of the HPH is 38 dB and the Noise Reduction Statistic (NRSA) (ANSI S12.68) (80% to 20% of users) is 45 to 52 dB. We also describe challenges associated with user acceptance of the HPH. User feedback led to the integration of an electronic hear-through system to restore auditory situational awareness. Users also rejected wired communication-enabled ear plugs, resulting in the integration of ear cup speakers and adding challenges associated with setting the hear-through sound pressure level limits. We conclude with anecdotes from trial deployments aboard U.S. Navy Aircraft Carriers in 2020, 2022, and 2023.

Validation of an image source method room acoustics software in a highly reverberant room with a directional impulsive noise source

Exposure to impulsive noise sources is common during routine operations military contexts. This type of noise exposure is prevalent in training procedures carried out with small caliber firearms in both indoor and outdoor settings. Typically, hearing protection is required to mitigate hearing damage risk to military personnel. Consequently, proper prescription of hearing protection required bioenvironmental engineers and industrial hygienists to travel and collect data in situ which can be time consuming and expensive. As such, the researchers at the 711th Human Performance Wing of the United States Air Force Research Lab have developed a software named the Shooting Range Impulse Noise Calculator (ShRINC). The ShRINC software provides the capability to simulate high fidelity acoustic levels within indoor and outdoor shooting ranges with directional impulsive noise sources. This is accomplished by leveraging principles from Image Source Room (ISM) based room acoustics and combining them with weapon source models with complicated directivity patterns. In this work, validation will be completed by comparing results collected in a highly reverberant facility with the M4A1 firearm operating blank rounds. An investigation into the proper order for the ISM solver will be analyzed and sound exposure levels between the simulation and measured data will be compared.

Awareness of Noise-Induced Hearing Loss among the General Population in the Eastern Province of Saudi Arabia

Abstract Introduction: Noise-induced hearing loss (NIHL) is a common work-related hazard that can affect employees and can lead to multiple health problems, and the use of hearing protection devices has been proven to reduce the possibility of developing NIHL. This study aims to construct useful knowledge that can be used to increase awareness campaigns and promote social acceptance of the use of hearing protection devices among the general population in the Eastern Province of Saudi Arabia. Materials and Methods This is a descriptive, cross-sectional study, and the convenience sampling technique was followed in this study, in which the questionnaire was distributed electronically through social media platforms. The questionnaire contained 18 items to evaluate NIHL and awareness of the effects of loud sounds on hearing and health. Results: Of the 416 respondents involved in the study, it was observed in this study that gender, level of education, and age were not significantly associated with a higher or lower perception of hearing loss. Forty-three percent of the study participants have not heard anything about hearing loss at all, and surprisingly, among the participants who have heard about it, only 4.8% of the participants stated that they obtained their information from medical campaigns, which is the least informative site for hearing loss information. Finally, it is shown that the majority of the participants, 52.2%, have not heard any information regarding earplugs. Conclusion: This paper provides data on noise exposure and its associations with the risk of hearing impairment and attitudes toward earplugs among the Saudi population in the eastern region. The results explicitly showed that the young age group demonstrated a low level of knowledge and a low level of awareness of NIHL and the importance of earplugs. As a result, we strongly advocate for more health campaigns to raise community awareness of NIHL.

Improving hearing protection compliance by optimizing user Mission Effectiveness

Traditionally intra-aural (ear plugs) and Circum-aural (muff) style HPD’s are provided in elevated noise environments to provide additional noise protection. With proper training around insertion and wearing, these devices are used to provide compliance with safety standards for hearing exposure. It is well understood that the wearer’s ACTUAL protection, in their work/mission roles, are regularly eroded by misuse due to user isolation from “wanted” or “needed” sounds: Situational awareness for safety or mission needs, and Ambient and/or needed communications Alternative technologies can be applied to enhance the users Mission Effectiveness. With that, they “want to” wear devices. These can be customized/personalized to fit their mission while provide appropriate protection. While the overall protection might not reach the levels “possible” with a clinical HPD application, users wear the devices properly, gaining significant and consistent overall protection. This paper will explore additional technologies available, to incorporate into Muff-type HPD’s, that will enhance user productivity while also improving hearing protection: Active noise reduction (FB and FF), Active/personalized audio compensation and HPD effectiveness testing, Noise dosing information, and Customized alerts for preset thresholds covering hearing and environmental hazards.

Influence of background noise on spatial audio localization for helicopter pilot headsets

A helicopter pilot is subjected to high workloads. A high noise level in the cockpit further increases stress. This stress can be reduced through headsets for hearing protection including active noise control (ANC). An actual research topic is the improvement of the human-machine-interface by 3-D-audio systems. These systems can improve pilot’s situational awareness and, therefore, reduce stress. This paper presents a 3-D-audio system for headphones. This binaural system uses head-tracking to process spatial information about the location of the sound source. The spatial sensation is achieved by convolving the source signal with head-related transfer functions. This sensation is influenced by background noise, which can be reduced by ANC. A first listening test with physical sound sources provides information on the localizability of sound sources at different elevation angles. This is compared to a second listening test with virtual sound sources generated by the 3-D-audio system. In a third listening test, the virtual sound source is located at variable azimuth and elevation angles. The system is evaluated with respect to sound source localization and the influence of background noise and ANC. This study highlights the potential of the 3-D-audio system to improve the helicopter pilot’s situational awareness in spatial acoustic environments.

The Effect of a Web-Based Occupational Noise-Induced Hearing Loss Prevention Program on Hearing Protection Device Behavior Among Thai Navy Officers: A Quasi-Experimental Study

Navy officers working on the coastal guard vessels risk hearing loss due to repeated exposure to high noise levels from ship engines. Therefore, proper use of hearing protection devices is important. In this study, a web-based hearing loss prevention program was developed to promote the behavior of the use of hearing protection devices among Thai navy officers working on coastal guard vessels. In total, 152 navy personnel were recruited based on selection criteria and randomly assigned to the experimental (n = 76) and control groups (n = 76). The participants in the experimental group received the hearing loss prevention program via a website over four weeks. After completing the program, hearing protection device behavior was evaluated by a self-report questionnaire immediately after and at eight weeks follow-up. The results showed significantly increasing scores of the use of hearing protection devices behavior within the experimental group, both immediately and eight weeks after the program completion. However, there were no significant differences in the scores when comparing between groups, even though the scores of the experimental group were better than those in the control group. The restrictions could be explained by some emerging events during the implementation period, including the COVID-19 pandemic followed by a massive oil spill incident at sea. These put an extra workload on the study participants. Most importantly, there was a problem with the network connection that might have affected the continuation of participant attention to the program. Although this study found no effective results of the developed program due to some limitations, nurses can adopt this protective intervention to reduce the risk of occupational noise-induced hearing loss among Navy officers. Therefore, a recommendation for further study is to develop an intervention program that considers both the working context of the coastal vessels and appropriate participation methods that require more challenging efforts.

Training to Improve Spatial Hearing andSituation Awareness when Wearing Hearing Protection.

Hearing protection devices (HPDs) are standard personal protective equipment in military settings, but many service members may choose to not use HPDs because they impair spatial hearing and situation awareness. In an effort to reduce barriers to compliance by improving situation awareness while wearing HPDs, this study investigated whether brief training could counteract spatial hearing deficits when wearing HPDs. Participant's ability to correctly apply the HPDs across days was also examined. Young adults were randomly assigned to one of two groups: training or control (n = 25/group). Participants in each group performed a spatial hearing task while wearing HPDs and in an open ear condition without HPDs. Individual targets were battlefield sounds or white noise presented from a speaker array that surrounded the participant in the horizontal plane. After presentation of each target sound, the participant then controlled a white noise "auditory pointer," which they moved to the perceived location of the target. The two primary measures were the percent of trials with very large errors (> 45°), which were usually due to confusing front and back locations, and absolute localization, which is the difference between the pointer location and the true sound location. Both groups were tested on Days 1 (baseline) and 5 (post-test). On Days 2 to 4, the training group wore HPDs while receiving auditory and visual feedback after each trial. Across all participants on Day 1, wearing HPDs increased the frequency of very large errors by about 3× and impaired localization by about 40%, relative to the open ear condition. When comparing performance at baseline (Day 1) and post-training Day 5, the training group with HPDs had significant reductions in very large errors and improved absolute localization (P values < .001). The training group also had significant improvements from Days 1 to 5 in the open ear condition. When the control group wore HPDs, there were also significant improvements from Days 1 to 5 (fewer very large errors and better localization), with smaller effect sizes vs. the training group. Controls did not have significant improvement in the open ear condition, but had similar trends. Most participants consistently applied the HPDs, but a subset of ∼20% frequently failed to achieve the criterion attenuation of 15 dB (over 0.25-4.0 kHz) in both ears. These findings show that simple, relatively brief practice and training can substantially reduce HPD impairments on spatial hearing and situation awareness. The gains from training and practice can inform the development of relatively simple, brief methods to reduce HPD spatial hearing impairments, potentially leading to increased HPD compliance. Longitudinal data show that a subset of participants would not have received the full benefit of hearing protection because of improper application of the HPDs.

A current affair: worker perceptions of noise exposure and occupational hearing loss in Australian coal mines.

The objective of the online survey was to determine worker attitudes towards, perceptions on hearing loss, and management of workplace noise; and to identify barriers within current strategies that prevent effective management of hearing health in Australian mines. This cross-sectional study utilized a modified survey design, initially designed for use by Safe Work Australia for a broader study published in 2010. The survey questionnaire was made available online to volunteer participants, recruited with the assistance of State and National Health and Safety, and mining organizations. Volunteer participants were required to be proficient in English, be employed by an Australian underground or open cut mine, including coal processing plants; or work as a contractor on one of the specified mine sites. All mining employees, regardless of occupation, job title, and occupational hearing loss classification or status, were invited to complete the questionnaire. Almost 60% of respondents indicated that they had high noise exposure for than 10 yr or more, and have some trouble hearing, mostly associated with infrequent tinnitus. Nearly 71% of these workers believe that the noise control strategies in their workplaces are effective, but this mostly refers to the use of hearing protection devices. The results indicate that general knowledge on the cause and effect of noise exposure in the workplace is well understood. However, due to the long latency associated with the development of noise-induced hearing loss (NIHL), there is an issue urgency in terms of risk management. It is surprising that most of the respondents recommended more inspections and administrative controls, especially since most respondents were health, safety, and environment (HSE) professionals. HSE professionals should be advocating for higher order, more permanent solutions, and not purely administrative controls and personal protective equipment. These findings raise the question of whether there is a multifaceted working-culture issue that needs to be addressed, in combination with higher order control implementation.

The significance of serum Klotho to hearing loss: a potential protector under noise pollution.

The issue of hearing protection in the presence of noise pollution is of great importance in the fields of environmental science and clinical medicine. Currently, the clinical significance of Klotho in relation to hearing has not been revealed. The aim of this study was to examine the correlation between serum Klotho levels and Pure Tone Average (PTA) hearing thresholds among individuals in the U.S.. The analysis involved a sample of 1,781 individuals aged 20 to 69, obtained from the 2007-2012 National Health and Nutrition Examination Survey. Various methods were utilized for the analysis, including univariate and multivariate linear regression, stratified analysis, smooth curve fitting, a two-segment linear regression model, and log-likelihood ratio analysis. The results of the univariate analysis indicated that serum Klotho concentration, age, education level, hypertension, diabetes, and smoking all exhibited a significant influence on PTAs. After adjusting for potential confounding factors, it was observed that a decrease in serum Klotho was significantly associated with PTA thresholds at low frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.004), speech frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.007), and high frequency (β = -0.002; 95% CI: -0.003, -0.001; P = 0.045). Specifically, for every 1pg/ml decrease in serum Klotho concentration, the PTAs increased by 0.002dB. Moreover, age and gender-specific analyses revealed significant associations. For individuals aged 59-69, a significant association was found between serum Klotho concentration and high-frequency PTA (β = -4.153; 95% CI: -7.948, -0.358; P = 0.032). Additionally, among females, significant associations were observed between serum Klotho concentration and speech-frequency PTA (β = -1.648, 95% CI: -3.197, -0.099; P = 0.037) as well as high-frequency PTA (β = -3.046; 95% CI: -5.319, -0.772; P = 0.009). Finally, the results of smooth curve fitting and threshold effect analyses indicated a potential negative linear correlation between serum Klotho concentration and PTA thresholds. In conclusion, a lower level of serum Klotho was found to be associated with increased hearing thresholds, particularly among the elderly population. This finding has significant implications for the prevention and treatment of hearing damage.

Managing occupational impulsive noise from explosive depth hardening operations

The assessment and identification of measures to eliminate or reduce risks from occupational exposure to impulsive noise for the protection of hearing of employees in industry is an important yet comparatively neglected technical area. The aim of this work is to examine the current best practice to assess auditory hazards associated with impulsive blast noise generated by an infrastructure test process at a UK-based test site. A summary of the literature is presented on the measurement methodologies, hearing conservation and relevant guidance for the selection of hearing protection within the context of near-field impulsive noise. The current UK best practice recommends the adapted HML method from Defence Standard 0027:2015, using a C-peak measurement of exposure to compare with the national regulations. On-site measurements of personnel exposure were made at the DNV Spadeadam Testing and Research Site (STaR), of an industrial process known as Explosive Depth Hardening. Analyses of the trials data show that the C-peak personnel exposures resulted in acceptable levels below the 140 dBCpk limit within the national regulations when using the prescribed hearing protection, according to the adapted HML method. Waveforms recorded of repeated charge sizes were uncorrelated and additional signal artefacts were present. It is concluded that the adapted HML assessment is unclear on how excessive low-frequency content and multiple pressure peaks are accounted for in the assessment of hearing protector performance. The implication of this work is that further research is required to improve current best practice to quantify the uncertainties introduced by the additional characteristics found within real impulsive noise exposures.

Risk perception or hazard perception? Examining misperceptions of miners' personal exposures to noise.

While perceptions of risk have been examined in the workplace to understand safety behavior, hazard perception has been overlooked, particularly for chemical, physical, and biological agents. This study sought to establish the prevalence of one type of mismatch in hazard perception, - noise misperception - among miners, to examine whether different types of noisy environments (e.g., continuous, highly variable, etc.) alter workers' misperception of their noise exposures, and to evaluate whether noise misperception is associated with hearing protection device (HPD) use behavior. In this cross-sectional study across 10 surface mines in the USA, 135 normal-hearing participants were surveyed on their perceptions of exposure to noise at work and were monitored for three shifts, each with personal noise dosimetry, to examine which workers had a mismatch in perceived versus true noise exposure by 8-hr, time-weighted average, NIOSH exposure limits (TWANIOSH). Mixed effects logistic regression and probit Bayesian Kernel Machine Regression (BKMR) models examining on the odds of noise misperception associated with four different noise metrics (kurtosis, crest factor, variability, and number of peaks >135dB) were used to determine which types of noisy environments may influence noise misperception. The relationship between noise misperception and odds of not wearing HPDs during a work shift was further examined. Our findings showed that nearly 1 in 3 workers underestimated their exposure to noise when their true exposure was in fact hazardous (TWANIOSH≥85 dBA) for at least one shift, and 6% misperceived hazardous exposures for all shifts. Work shifts with highly kurtotic noise distributions (>3) had 3.1 (95% CI: 1.1 to 8.4) times significantly higher odds of resulting in misperceived noise; no other noise metric was significantly associated with noise misperception. BKMR modeling provided further evidence that kurtosis dominates this relationship, with an IQR increase in kurtosis significantly associated with 1.68 (95% CI: 1.13 to 2.50) higher odds of noise misperception. Although not statistically significant, misperception of hazardous noise exposure was associated with 3.2 (95% CI: 0.8 to 12.5) times higher odds of not using earplugs during a work shift. Misperception of noise occurs in the workplace, and likely occurs for other physical, chemical, and biological exposures. This hazard misperception may influence risk perceptions and worker behavior and reduce the effectiveness of behavior-related training. Elimination, substitution, or engineering controls of exposures is the best way to prevent hazard misperceptions and exposure-related diseases.

Hearing protection of noise-cancelling earphones in dental clinics

Hearing protection of noise-cancelling earphones in dental clinics

Long-Term Hearing Loss after Acute Acoustic Trauma inthe French Military: A Retrospective Study.

Acute acoustic trauma (AAT) is characterized by cochlea-vestibular signs following intense noise exposure, often caused by impulse noise. French military faces a high risk of AAT because of the use of weapons with peak sound levels exceeding 150 dB. Hearing loss (HL) resulting from AAT can have a significant impact on quality of life and operational capacity. The aim of this study was to assess the prevalence of long-term hearing impairment after AAT. The study involved a retrospective review of computer-based patient records from four military medical centers in Northeast France between January 2016 and December 2021. The inclusion criteria required the presence of cochlea-vestibular signs following impulse acoustic exposure and the absence of other causes. Sociodemographic and clinical data were collected, including audiometric data before and after exposure. The primary end point was the presence of a threshold elevation greater than 10 dB between reference and late audiograms. A total of 419 patients were included in the analysis, with a majority of males (n = 419; 84.7%) and a mean age of 23.6 yrs. The most common causative agent was the 5.56-mm assault rifle (n = 327; 78.0%). Tinnitus was the most frequent symptom (n = 366; 87.4%), followed by hypoacusis (n = 147; 35.1%) and earache (n = 89; 21.2%). The initial audiograms showed no HL in 31.0% of cases, while the mean deficit across all frequencies was 15.4 dB. All patients received corticosteroid therapy, with a mean duration of 6.0 d. Late audiograms conducted at an average interval of 448.0 d after AAT revealed a prevalence of long-term HL exceeding 20%. Higher doses of corticosteroid therapy (>1 mg/kg) were associated with a reduced frequency of long-term HL. This study highlights the prevalence of long-term hearing impairment after AAT in the French military. The findings emphasize the importance of preventive measures, including proper use of hearing protection devices, and the need for timely diagnosis and treatment. Further research is warranted to explore gender susceptibility to AAT and evaluate the impact of different weapons on AAT characteristics. The study also underscores the potential benefits of higher doses of corticosteroid therapy in reducing the risk of long-term hearing impairment. Overall, the findings contribute to a better understanding of AAT and can inform strategies for its prevention and management in military settings.

A Study on the Hearing Protection Effect of Noise-Filtering Earplugs for Dentists

The aim of this study is to evaluate the effect of noise-filtering earplugs on the hearing ability of dentists wearing them during noise-induced dental procedures. Pure tone audiometry and distortion product otoacoustic emission (DPOAE) tests were conducted at the initial visit and 1 year later to evaluate the hearing ability of the participants. As a result of the study, the pure tone average of the group wearing earplugs decreased significantly compared to the group not wearing earplugs, indicating an improvement in hearing. However, the signal-to-noise ratio of the DPOAE tests did not show a significant difference. These findings suggest that noise-filtering earplugs may have some effectiveness in preventing hearing loss. However, since the 1-year observation period may not be adequate to identify changes in hearing, a follow-up study with an extended follow-up period is necessary.