Hearing Protection Research Articles

Measurement of Noise Intensity in the Al-Mahirah Lamdingin Market Area, Banda Aceh City in 2024

Introduction: Noise is a fairly important issue, especially in relation to comfort. Excessive noise levels in markets can have very dangerous negative impacts in many ways, namely health impacts as well as psychological and technical impacts. Objective: The purpose of this study is to identify the noise level that occurs in the market area using a Sound Level Meter (SLM) and to map the noise level in the Al-mahirah Lamdingin market. Methods: This study uses an observation method, data collection is carried out by direct observation and measurement of the research object. The sample in this study is one of the sectors of the community trade center, namely the Al-Mahirah Lamdingin market in Banda Aceh city which consists of 93 kiosks with 639 traders. Inclusion criteria are places where people often gather and pass by, areas that are flanked by lots of noise and come from different sources and machines that operate more than 4 hours in 1 day. Exclusion criteria are locations/areas that do not have noise sources and are far from the main road shoulder, machines that operate for less than 4 hours and operate only at certain times. Data were analyzed using Microsoft Excel software. Results: The results of the study showed that the noise intensity at the Al-Mahirah Lamdingin Market was already in the risky category because it had the highest noise intensity of 55.2 dBA, but did not exceed the threshold value that had been set, namely 65 dBA. Conclusion: Based on the measurement of noise intensity in the Al-Mahirah Lamdingin market, the noise intensity value does not exceed the noise quality standard value but is already at a risky stage because the measurement results are close to the set quality standard and the frequency and time of noise exposure are quite long with the target group. It is necessary to carry out control at each point such as changing the layout of the machine so that the noise does not collect in one place and the use of Hearing Protection Equipment (APT) or it can be by controlling the device, be it equipment renewal or repair.

Parametry akustyczne ochronników słuchu i metody ich pomiaru

Acoustic parameters of hearing protectors and methods of their measurement The article presents how the basic parameter of hearing protectors, i.e. sound attenuation, is determined using a method based on the active participation of people (subjective method). In addition, objective methods for measuring acoustic parameters of hearing protectors, such as insertion loss, based on the use of miniature microphones and acoustic test fixture are described. The results of measurements of sound pressure level under hearing protectors carried out using an acoustic test fixture reproducing anatomical shape of a human head (including concha and ear canal), used as a standard for measuring acoustic parameters of hearing protectors in impulse noise situations are also presented. These measurements were carried out to verify the possibility of using this acoustic test fixture, to measure the sound pressure level reaching under the hearing protectors in the case of continuous noise. The tests showed that in the case of measurements with microphones that are standard equipment of the acoustic test fixture, dedicated to impulse noise, the use of these microphones is limited to high-level continuous signals. Microphones that are optional equipment on the acoustic test fixture were a more suitable solution for the intended purpose.

Associations Between Noise Exposure Level, Noise Kurtosis, and Distortion Product Otoacoustic Emissions in Young Workers With Normal Hearing.

Growing evidence has suggested that, in addition to noise exposure level, noise temporal structure (i.e., kurtosis) plays an important role in the development of noise-induced hearing loss, while most of the relevant research has been on the results of pure-tone audiometry. This study focuses on the combined effect of noise exposure level and noise kurtosis on distortion product otoacoustic emissions (DPOAEs) in young workers with normal hearing. A cross-sectional study among young workers in manufacturing industries was conducted in Zhejiang Province, China. Individual noise exposure measurements were performed on participants to obtain an A-weighted noise exposure level normalized to 8 hr (LAeq, 8hr), cumulative noise exposure (CNE), kurtosis, and kurtosis-adjusted CNE (CNE-K). The DPOAE test was performed on the participants and DPOAE levels were obtained. The relationships between noise exposure level, kurtosis, and DPOAE levels were explored by univariate analyses. Furthermore, multivariate regression models were conducted to estimate the combined effects of exposure level and kurtosis after adjusting for age, gender, and use of hearing protection devices. The overall DPOAE curves across frequency bands presented a fluctuating downward trend with increasing frequency. Both exposure level and kurtosis were found to be associated with decreases in DPOAE levels. The multivariate regression model including CNE-K as a joint indicator of complex noise showed an increased R2 compared with the model including CNE. After adjustment for age, gender, and the use of hearing protection devices, significant effects of CNE-K on DPOAE levels were observed at 3, 4, and 5 kHz frequencies, with maximum effect presented at 4 kHz. DPOAE is a sensitive test that can detect cochlear damage in limited areas that cannot be detected by conventional audiometry. The present study provided a more comprehensive understanding of the impact of complex noise on the DPOAE levels. It also suggested that CNE-K was an effective metric in assessing DPOAE levels associated with complex noise.

Effects of the earplug and external ear hardness of the direct transmissions induced by high-level impulse noises

The performances of Hearing Protection Devices (HPD) facing high-level impulse noises is limited by the transmission through the protector. This transmission can be evaluated by measuring the earplug's displacement along the ear canal axis. Previous measurements highlighted a displacement proportional to the peak acoustic pressure in the protected ear canal. To better understand the consequences on the HPD performances, this evaluation requires to be extended. Thus, various configurations are studied with Acoustic Test Fixture (ATF) external ears and earplugs of low and medium hardness. The earplug's peak displacements have been measured with a laser-vibrometer and the acoustic pressure with the ATF microphone. The impulse waves employed to excite the earplugs ranged from 150 dB to 180 dB peak. A medium hardness earplug inserted in a low hardness ear led to the worst performances with a plug displacement of 200 µm and a peak noise reduction of 17.8 dB(SPL) for an impulse noise of 177 dB(SPL). For the best case, a maximum displacement of 66 µm and peak noise reduction of 28.8 dB(SPL) have been measured. These results suggest new perspectives to improve the HPDs but also their evaluation through the choice of judicious ATF materials that conform to biological tissues.

Predicting the acoustic attenuation of dual protection

When workers are subjected to very high noise levels, one way of protecting their hearing is to use dual protection, i.e. to wear earplugs and earmuffs simultaneously. The literature shows that the acoustic attenuation provided by a dual protection is much lower than the sum of the acoustic attenuations provided by each of the hearing protectors, but it does not propose any method for evaluating it, which poses a risk to safety. A review of the literature was undertaken. The acoustic attenuations of a number of combinations were collected. At the same time, tests were carried out on four combinations, in order to supplement the relatively old data in the literature with up-to-date data. On the basis of this data set, formulas were established to calculate the octave-band attenuations of the combination of two protection devices from their respective attenuations. The overall attenuation indices (SNR, H, M and L) can be deduced to select hearing protectors according to noise exposure. These indices are predicted with good accuracy, less than 3dB. This work will enable occupational health and safety professionals to assess the protection provided by dual protection, and thus to recommend it in a fully safe way.

Study of the acoustic attenuation of 2D axisymmetric models of the human ear equipped with hearing protection

The ear is the organ responsible for auditory perception. Its role is to amplify, transmit, and convert an acoustic wave present in the environment into an electrical pulse that the brain can interpret via the auditory nerve. The objective of this study was to develop two axisymmetric 2D finite element models of the human ear to predict insertion loss when a porous earplug is introduced into the ear canal. In these models, the structure-acoustic interaction was resolved by finite element analysis. For a better representation, assumptions and boundary conditions (such as fixe boundary condition, spring-mass-damping boundary condition, etc...) are considered. The tympanic ring and the earplug are assumed to be fixed, and a load of what comes after the posterior part of the tympanic ring (the ossicular chain) has been replaced by an equivalent mechanical impedance mass-spring-damper system. The first model has a regular geometry, and the second model is obtained by reconstructing a 3D model. These two models were inspired by our previous work. For each model, the insertion loss (IL) is predicted and the results obtained are compared with those of the sound attenuation measurements of hearing protection performed in the laboratory.

Design, optimization and validation of a small cabin for standardized objective measurements of earmuffs and earplugs on artificial head (ATF) according to ISO4869-3

The attenuation of hearing protection devices is currently mainly measured using the REAT (ISO 4869-1) standardized subjective method. However, during the development step, manufacturers need to carry out a numerous tests quickly making the REAT method unsuitable due to its need of a large number of subjects with associated training time and represents a significant cost. As an alternative, the standardized objective method (ISO 4869-3) uses an artificial head (ATF) in a controlled acoustic environment. Delta Plus called on CTTM to provide a test facility compliant with the 4869-3 standard, and designed with reduced dimensions to fit easily into its test laboratory. The presented work describes the steps of design, development and validation of a measuring cabin meeting these requirements. The search for a suitable geometry for the cabin volume is based on numerical modeling using boundary elements. The cabin, built using this initial approach, is then empirically optimized using different types of diffusers to meet sound field homogeneity criteria. Comparisons of measurements made using both subjective (ISO 4869-1) and objective (ISO 4869-3) methods are presented at the end.

Revision of Japanese guidelines for the prevention of noise-induced impairments in 2023

In Japan, the guideline for the prevention of noise-induced impairments published in 1984 was revised in 2023. The revisions include changes to the definition of target workplaces, methods for measuring noise levels, and methods for selecting hearing protection equipment. Additionally, prior to the revision of the guidelines, Japanese industrial standard (JIS) regarding the method for measuring the sound attenuation performance of hearing protectors was established in 2020. The old JIS was a product standard, but it was changed to a method standard with the ISO standard as an international standard. The new JIS has adopted single number rating (SNR) as an evaluation index. In recent years, Japan's guidelines and standards related to occupational noise have been internationally harmonized, but currently they are only published in Japanese. In this paper, an overview of the guidelines for the prevention of noise-induced impairments revised in 2023 will be mainly presented. This paper also introduces measuring device for noise exposure level, fit testing equipment, and real-ear attenuation at threshold (REAT) testing currently available in Japan. An overview of the new JIS was previously reported at inter-noise conference in 2021.

Novel methods for the control of blast noise from explosive depth hardening

DNV Spadeadam undertakes crucial major hazards testing to improve safety across a wide range of industries, including energy and infrastructure. One common form of testing is Explosive Depth Hardening (EDH) in which plastic explosives up to 10 kg TNT are used to harden pre-cast railway crossings in order to support national transport infrastructure. The operations produce extremely high intensity noise and are carried out up to 10 times per day. The source characteristics of the explosion are not well understood and vary significantly with operational demands. This has implications on occupational and environmental blast noise impacts. Quantification of the source characteristics are important for the exposures of site personnel with regards to providing adequate hearing protection. Moreover, for the purpose of managing environmental noise impacts on local communities, the uncertainties around source directivity and strength make long-range blast noise prediction difficult. This paper presents the current research on novel blast noise mitigation undertaken in the laboratory, such as experimental water curtains, water sprays, and metamaterial designs. It is proposed to implement novel methods developed in the laboratory for use during EDH shots at full-scale, and the potential improvements to occupational and environmental noise impacts will be discussed.

Consideration and case study using a time-difference-of-arrival directional device for occupational noise measurement

To protect worker's hearing in noisy workplaces, noise levels are measured periodically, and noise sources are located based on the results of recordings or video cameras. If the noise level is above a certain level, noise abatement measures are taken, or workers are suggested to wear hearing protection. Measuring the noise level can be done simply by placing a sound level meter on the floor, but finding the noise abatement is a time-consuming task. It is necessary to listen to the recordings one by one or review the video to find the noise abatement. We believe that a simple method of estimating noise abatement is very useful, since some noisy workplaces do not allow recordings or video cameras for privacy and confidentiality reasons. In this paper, noise source identification using a time-difference-of-arrival directional device in an indoor environment is examined. The results are analyzed in the context of room properties such as reverberation time, dimensions, and device localization. The paper also reports on practical use-cases in actual sites.

Assessment of transparent alternative listening devices' effects on localization cues using head-related transfer function measurements

The past few years have seen a meteoric rise in technological advancements in the hearing health industry. New alternative listening devices, often referred to as "hearables", aim to become real "bionic ears" offering hearing protection, amplification, monitoring and even biosensing functionalities. With the recent approval of the "Over-the-Counter Hearing Aid Act" in the United States and the introduction of so-called "OTC" hearing aids, these alternative listening devices now have the potential to revolutionize the world of traditional auditory amplification. Since these devices may be used by individuals with hearing loss, it is important to consider how they might influence spatial auditory awareness. Therefore, this paper studies the effect of alternative listening devices on localization cues using the Head Related Transfer Function (HRTF). In this purpose, we measured the HRTFs on a Head and Torso Simulator (HATS) with and without digital listening devices. To evaluate the acoustic performance of these devices, the devices were set into their "acoustically transparent" mode. These measures enable a preliminary characterization of the effect of hearables and OTC devices on localization cues.

Practical considerations for assessing crew noise exposure in armored vehicles.

Measurement and analysis of the continuous and intermittent noise produced by armored vehicle (AV) platforms, including the output from communications systems as experienced by crew, are necessary for the purposes of exposure prediction, to support the selection of hearing protection and communication devices, and to facilitate assessments of compliance with occupational health and safety legislation. Practical estimation of the personal noise exposure of AV crews requires the assessment of the vehicle, communications and special-to-role activity noise sources, and an understanding of how these sources combine. Procedures are described that consider instrumentation requirements, AV configuration and build standard, operating conditions representative of actual use, the application of speed thresholding to measurements, and derivation of communications noise levels. Real-world examples are given where these procedures have been applied to an in-service tracked AV to estimate crew noise exposure. The procedures and methods presented are a compromise between precision, repeatability, reproducibility, and pragmatism. Measurements of AV noise are expected to be obtained during the commissioning stage of vehicle design, immediately prior to the vehicle being put into operational service and following any major modifications to the vehicle to inform the necessary engineering, administrative, and personal protective equipment control measures.

An Adult with Congenital Aural Atresia, Amplification, and Exaggerated Hearing Difficulty with Use of Hearing Protection

An Adult with Congenital Aural Atresia, Amplification, and Exaggerated Hearing Difficulty with Use of Hearing Protection

Amitriptyline protects afferent synapses in the cochlea against excitotoxic trauma in vitro.

Afferent synapses between inner hair cells (IHCs) and the type I spiral ganglion neurons (SGNs) in the cochlea provide over 95% of sensory signals for auditory perception in the brain. However, these afferent synapses are particularly vulnerable to damage, for example from excitotoxicity, and exposure to noise in the environment which often leads to noise-induced cochlear synaptopathy (NICS). In this study, we simulated excitotoxic trauma by incubating kainic acid, a non-desensitizing agonist for AMPA type glutamate receptors on cultured cochleae. The possible protective effects of amitriptyline against NICS were examined. We found that, in IHCs, amitriptyline reversed the decrease of Ca2+ current and exocytosis caused by excitotoxic trauma. In SGNs, amitriptyline promoted the recovery of neurite loss caused by excitotoxic trauma. Furthermore, we found that the protective effects of amitriptyline are likely mediated by suppressing apoptosis factors that were upregulated during excitotoxic trauma. In conclusion, our results suggest that amitriptyline could protect afferent synapses in the cochlea from NICS, making it a potential drug candidate for hearing protection.

Measurement and evaluation of personal attenuation rating before and after the training of the noise-exposed workers wearing foam earplugs

Objective: To measure and compare the difference of personal attenuation rating (PAR) of the workers wearing foam earplugs before and after the training, and to evaluate the effect of ear protector wearing training on the noise protection. Methods: In February 2023, 94 workers exposed to noise in a machinery manufacturing factory were selected as subjects. The production noise in the workplace was measured and subjects were trained to wear earplugs. The PAR values of wearing 3M 1110 foam test earplugs were measured and recorded before and after the training by using the fit testing of hearing protection device. The differences between the actual PAR values with nominal values and the noise attenuation values in related standards were compared, and the protective effect of hearing protection device before and after training was evaluated. Results: The average age of the subjects was (36.76±11.48) years old, the average length of service was (16.34±11.64) years, and the average exposure time to noise was (15.67±11.64) years. The noise detection results of the subjects' posts were ranged from 80.1 to 94.3 dB (A). The results of subjects wore 3M 1110 foam test earplugs for fit testing showed that the binaural PAR value after training was (19.3±6.4) dB (A), which was significantly higher than that before training (11.1±7.4) dB (A) (t=13.31, P<0.001). After training, 11 people (11.70%) could reach the corrected noise reduction value (NRR value), 26 people (27.66%) could reach the standard of single noise reduction value (SNR value) ×0.6, and 84 people (89.36%) could reach the standard of (NRR-7) /2. The under protection rate of hearing protectors after training (7.45%) was significantly lower than that before training (45.74%), and the difference of different protection levels before and after training was statistically significant (χ(2)=40.83, P<0.001) . Conclusion: It is suggested that enterprises should use the fit testing instead of nominal value estimation to evaluate the noise reduction effect of hearing protection device. Special training on the selection and use of hearing protection device should be strengthened, so as to ensure that workers wear them correctly and improve the protective effect of hearing protection device.

Auditory System Injury on the Battlefield-Solutions for Point-of-Injury and Prolonged Casualty Care: A DOTmLPF-P Analysis.

"Good hearing" (DoDI 6030.03 6.5&6.6) is a combat multiplier, critical to service members' lethality and survivability on the battlefield. Exposure to an explosive blast or high-intensity continuous noise is common in operational settings with the potential to compromise both hearing and vestibular health and jeopardize safety and high-level mission performance. The Joint Trauma System Acoustic Trauma Clinical Practice Guideline was published in 2018, providing recommendations for the assessment and treatment of aural blast injuries and acoustic trauma in the forward deployed environment. Combat care capabilities responsive to current threat environments emphasize prolonged casualty care. Despite recommendations, auditory system health has not been assessed routinely or in its entirety on the battlefield. This is due primarily to the large footprint of an audiometric booth and to the heavy logistical burden of providing high-quality, comprehensive auditory system (including vestibular) examinations in the combat environment. The Defense Health Agency Hearing Center of Excellence has completed a Doctrine, Organization, Training, Materiel, Leadership & Education, Personnel, Facilities, and Policy (DOTmLPF-P) analysis of battlefield auditory system assessment and treatment, using 67 existing DoD documents and artifacts related to operational medicine. Our analysis found that acoustic trauma is generally not addressed in any of the DOTmLPF-P domains. We recommend that auditory system assessment and treatment be incorporated across the continuum of care on the battlefield. This should be addressed through Prolonged Field Care and Tactical Combat Casualty Care guidance and in all Tactical Combat Casualty Care training programs. Equipment sets should be modified to include boothless technology and associated materiel for auditory system assessment. Policy and Doctrine changes would be required to mandate and support the implementation of these services. Uniformed audiologists should be added to the organizational structure at role 3 or higher to provide direct patient care; consult with other health care providers and commanders; develop and support enforcement of noise hazard guidelines; track hearing readiness; and, when necessary, provide specialized hearing protection devices that can compensate for hearing loss. These recommendations aim to help the DoD bring about necessary assessments and interventions for acoustic trauma so that service members can have better hearing outcomes and maintain critical auditory system function on the battlefield.

Hearing Loss and Cognitive Impairment Among Community-Dwelling Older Adults - Liaoning, Henan, and Guangdong Provinces, China, 2019-2020.

Many studies have shown that hearing loss (HL) is a risk factor for cognitive decline and dementia, but there are still limited studies on this association among Chinese older adults. Based on the results of pure-tone audiometry tests, HL is associated with cognitive impairment in community-dwelling older adults. The odds ratios (ORs) were 1.23 (1.08-1.40) for mild HL, 1.55 (1.32-1.82) for moderate HL, and 1.87 (1.47-2.39) for severe or profound HL. Enhanced public awareness of hearing protection is important for preventing cognitive impairment. It is advocated to promote the screening of HL and cognitive function assessment in elderly health examinations or management in primary care services.

Noise disturbance increases negative emotions and unsafe behaviour among construction workers

Construction works and activities generate a high level of noise, which can have a negative impact on workers. Prolonged exposure to noise disturbance can result in psychological changes, such as reduced awareness, and physical changes, such as hearing impairment, in workers, which affect their behaviour. Coupled with negative emotions, noise disturbance can magnify workers’ unsafe behaviour. Adopting a case study research design, this research collected noise level data from an apartment project in Surabaya, Indonesia, and used a questionnaire survey to assess the level of noise disturbance, and workers’ negative emotions and unsafe behaviour in the project. The research found that the noise levels, particularly for structural works, were generally beyond the advisable threshold specified in the government’s regulation. As a result, workers who performed structural works experienced higher noise disturbance and more negative emotions, and tended to display more unsafe behaviour than workers who performed finishing works. The research also found that noise disturbance increases negative emotions and unsafe behaviour among construction workers. In addition, the result indicates that negative emotions can mediate the relationship between noise disturbance and unsafe behaviour. Managing noise levels, therefore, can be a strategy worth implementing to improve health and safety in construction projects. Furthermore, requiring workers to wear a hearing protection device is not adequate for construction noise management. Involving mitigation strategies higher in the hierarchy of risk controls is needed for this purpose.

Prevalence and Factors Associated With Occupational Noise-Induced Hearing Loss Among Palm Oil Mill Workers in Selangor, Malaysia.

Introduction Occupational noise-induced hearing loss (NIHL) continues to be a significant public health issue globally, with Malaysia being no exception. In Malaysia, the majority of NIHL cases are reported from the manufacturing sector, with Selangor among the states with the highest number of confirmed cases. This study aimed to assess the prevalence of and factors associated with occupational NIHL among palm oil mill workers in Selangor, Malaysia. Methods A cross-sectional study was conducted to analyze the data from the data collection form, noise risk assessment reports, and audiometric test results done between 2021 and 2022 with a comparable baseline audiometric test. Results A total of 143 participants from three palm oil mills joined this study. The prevalence of NIHL was 42.7% (n = 61). Following the logistic regression model, NIHL was significantly associated with a duration of employment of 10 years and above, a history of occupational noise exposure at the previous workplace, and the use of personal hearing protectors at the current workplace with an adjusted OR of 2.41 (95% CI (1.14, 5.07)), 5.89 (95% CI (2.38, 14.53)), and 0.36 (95% CI (0.16, 0.83)), respectively. Conclusion The prevalence of NIHL among the study participants was high, and the associated factors are modifiable factors that can be prevented with a comprehensive hearing conservation program in the palm oil mills.

A longitudinal study investigating the effects of noise exposure on behavioural, electrophysiological and self-report measures of hearing in musicians with normal audiometric thresholds

Musicians are at risk of hearing loss and tinnitus due to regular exposure to high levels of noise. This level of risk may have been underestimated previously since damage to the auditory system, such as cochlear synaptopathy, may not be easily detectable using standard clinical measures. Most previous research investigating hearing loss in musicians has involved cross-sectional study designs that may capture only a snapshot of hearing health in relation to noise exposure. The aim of this study was to investigate the effects of cumulative noise exposure on behavioural, electrophysiological, and self-report indices of hearing damage in early-career musicians and non-musicians with normal hearing over a 2-year period. Participants completed an annual test battery consisting of pure tone audiometry, extended high-frequency hearing thresholds, distortion product otoacoustic emissions (DPOAEs), speech perception in noise, auditory brainstem responses, and self-report measures of tinnitus, hyperacusis, and hearing in background noise. Participants also completed the Noise Exposure Structured Interview to estimate cumulative noise exposure across the study period. Linear mixed models assessed changes over time. The longitudinal analysis comprised 64 early-career musicians (female n = 34; age range at T0 = 18–26 years) and 30 non-musicians (female n = 20; age range at T0 = 18–27 years). There were few longitudinal changes as a result of musicianship. Small improvements over time in some measures may be attributable to a practice/test-retest effect. Some measures (e.g., DPOAE indices of outer hair cell function) were associated with noise exposure at each time point, but did not show a significant change over time. A small proportion of participants reported a worsening of their tinnitus symptoms, which participants attributed to noise exposure, or not using hearing protection. Future longitudinal studies should attempt to capture the effects of noise exposure over a longer period, taken at several time points, for a precise measure of how hearing changes over time. Hearing conservation programmes for “at risk” individuals should closely monitor DPOAEs to detect early signs of noise-induced hearing loss when audiometric thresholds are clinically normal.