Assessment Of Noise-induced Hearing Loss Research Articles

Assessment of noise-induced hearing loss (NIHL) of weaving factory workers in West Bengal, India - a pilot study

Introduction: Excessive noise exposure is one of the majorly considered occupational stress for industrial workers. The operation of steel weaving machinery producing a high level of noise such as weaving machines, crimping machines, and hydraulic press machines for a prolonged period increases the risk of developing noise-induced hearing loss (NIHL). The main aim of the study was to assess the auditory health of the workers exposed to a high level of noise in a steel weaving factory and the prevalence of NIHL among workers. Methods: 26 subjects in the age group of 25-55 years from a steel weaving industry of Chinsurah town, Hooghly district of West Bengal were randomly selected with 5 years of exposure for the study. The control group was selected from the same age group, socioeconomic status and geographical location and having no history of such exposure. The physiological parameters of the workers, noise levels in the workplace and auditory functions and the risk of NIHL were assessed by standardized protocol and statistically analyzed. Results: The study indicated that steel weaving factory workers had significantly reduced hearing functionality at 4000Hz and 6000Hz in the left ear respectively. It also revealed that the workers were exposed to high noise exposure of 131dB near weaving machine, 113dB at crimping machine, and 84dB at hydraulic press machine respectively. Conclusion: A high level of noise exposure leads to deterioration in the hearing capabilities of the steel weaving industrial workers. Implementation of ergonomic interventions in the workplace and the use of personal protective equipment (PPE) may decrease the prevalence of NIHL and can help to prevent hearing loss in workers.

Risk assessment of noise-induced hearing loss among workers in railway transportation equipment manufacturing enterprises

To analyze the noise exposure and hearing loss of workers in railway transportation equipment manufacturing enterprises, and to assess the risk of hearing loss caused by noise. From 2018 to 2020, an investigation was carried out on 3 railway transportation equipment manufacturing enterprises in Hubei Province and Hunan Province. A total of 840 noise-exposed workers were selected, the individual noise exposure level(L_(Aeq·8 h)) and hearing loss level were measured, the cumulative noise exposure(CNE) was calculated, and the relationship between hearing loss and technological process, working time and CNE were analyzed. ISO1999:2013 was used to calculate the change of hearing threshold and the risk of noise-induced hearing loss after 40 years old. The median age of workers was 32 years old, and the median working age for noise exposure was 10 years. The distribution of positions is mainly welding, machining, assembly and painting.79.5%(120/151) of the individual noise exposure doses exceeded 85 dB(A), and the average L_(Aeq.8 h) was 89.9(A). There were significant differences in the proportion of hearing loss among workers in different process units(χ~2= 29.597, P<0.001), and the proportion of hearing loss in the preparation and steel structure units was higher. The proportion of hearing loss showed an upward trend with the increase of working years(χ~2=164.462, P<0.001), and the high-frequency combined speech-frequency hearing loss(26.7%) increased significantly after working for more than 20 years. With the increase of CNE, the proportion of high-frequency hearing loss and the proportion of high-frequency combined speech-frequency hearing loss increased accordingly(χ~2=192.544, P<0.001). The proportion of high frequency combined speech frequency hearing loss increased significantly in the group with CNE greater than 105 dB(A)·years. It is predicted that the risk of hearing loss caused by noise in assemblers appears earliest and the risk is the greatest. The risk of high noise-induced frequency hearing loss of assemblers was 3.6%-8.6% at the age of 40, 20.2% at the age of 50, 22.0% at the age of 60. The risk of high-frequency combined speech-frequency hearing loss of assemblers was 1.2%-6.2% at the age of 50 and 8.6% at the age of 60. The noise hazard is serious and widely distributed in railway transportation equipment manufacturing enterprises, and the proportion of hearing loss increases with the increase of working time and CNE. Although ISO1999:2013 predicts that there may be an underestimation of noise-induced hearing loss in workers, it can be used as an early warning of hearing loss to identify the potential risk of hearing loss in the population.

Noise Induced Hearing Loss and Tinnitus-New Research Developments and Remaining Gaps in Disease Assessment, Treatment, and Prevention.

Long-term noise exposure often results in noise induced hearing loss (NIHL). Tinnitus, the generation of phantom sounds, can also result from noise exposure, although understanding of its underlying mechanisms are limited. Recent studies, however, are shedding light on the neural processes involved in NIHL and tinnitus, leading to potential new and innovative treatments. This review focuses on the assessment of NIHL, available treatments, and development of new pharmacologic and non-pharmacologic treatments based on recent studies of central auditory plasticity and adaptive changes in hearing. We discuss the mechanisms and maladaptive plasticity of NIHL, neuronal aspects of tinnitus triggers, and mechanisms such as tinnitus-associated neural changes at the cochlear nucleus underlying the generation of tinnitus after noise-induced deafferentation. We include observations from recent studies, including our own studies on associated risks and emerging treatments for tinnitus. Increasing knowledge of neural plasticity and adaptive changes in the central auditory system suggest that NIHL is preventable and transient abnormalities may be reversable, although ongoing research in assessment and early detection of hearing difficulties is still urgently needed. Since no treatment can yet reverse noise-related damage completely, preventative strategies and increased awareness of hearing health are essential.

Improvement of noise-induced hearing loss criteria and occupational risk assessment

The analysis of the medical and social aspects of occupational noise-induced hearing loss (NIHL) on the basis of its phenomenology is presented. The ear as an information receiver and frequency range of voice communication are considered. The NIHL classifications in Russia, starting with GOST 12.4.062-78 are described, and an overview of international (WHO, 2011; ILO, 2013; UKOOA, 2003) and national (Belgium, France, USA) NIHL criteria are outlined. As example a civil aviation pilot audiogram was compared to different criteria; it is shown that in 5 of 14 models used criteria were stricter than GOST 12.4.062-78. It is noted that for the medical fitness to work examination it is necessary to use criteria that differ from those for population. The modification of GOST 12.4.062-78 classification is proposed by subdivision of signs of the noise influence on the hearing into 2 groups: early and expressed signs with NIHL values at 4 kHz less than 20 dB and 20-40 dB, respectively, that is useful for monitoring and prevention. The use of PPE with a view to ensuring safety is considered. The proposal to improve NIHL evaluation criteria are proposed in connection with the adoption of SanPiN 2.2.4.335916 onphysical factors with PEL of noise and GOST R ISO 1999-2017 on assessment of noise-inducedhearing loss, taking into account the role of hearing health for safe and effective work.

Occupational Hearing Loss from Non-Gaussian Noise.

Noise levels are truly continuous in relatively few occupations, with some degree of intermittency the most common condition. The sound levels of intermittent noise are often referred to as non-Gaussian in that they are not normally distributed in the time domain. In some conditions, intermittent noise affects the ear differently from continuous noise, and it is this assumption that underlies the selection of the 5-dB exchange rate (ER). The scientific and professional communities have debated this assumption over recent decades. This monograph explores the effect of non-Gaussian noise on the auditory system. It begins by summarizing an earlier report by the same author concentrating on the subject of the ER. The conclusions of the earlier report supported the more conservative 3-dB ER with possible adjustments to the permissible exposure limit for certain working conditions. The current document has expanded on the earlier report in light of the relevant research accomplished in the intervening decades. Although some of the animal research has supported the mitigating effect of intermittency, a closer look at many of these studies reveals certain weaknesses, along with the fact that these noise exposures were not usually representative of the conditions under which people actually work. The more recent animal research on complex noise shows that intermittencies do not protect the cochlea and that many of the previous assumptions about the ameliorative effect of intermittencies are no longer valid, lending further support to the 3-dB ER. The neurologic effects of noise on hearing have gained increasing attention in recent years because of improvements in microscopy and immunostaining techniques. Animal experiments showing damage to auditory synapses from noise exposures previously considered harmless may signify the need for a more conservative approach to the assessment of noise-induced hearing loss and consequently the practice of hearing conservation programs.

Guidelines for quantification of noise-induced hearing loss in a medicolegal context.

Guidelines published in 2000 by the authors are widely used by medical and legal professionals in the UK for diagnosis of noise-induced hearing loss in a medicolegal context. However, they cannot be used for quantification of the noise-induced hearing loss, which is required in most cases. This requirement is addressed. A method is developed here to quantify noise-induced hearing loss, thereby overcoming this shortcoming. Assessment of noise-induced hearing loss in medicolegal cases. A consecutive series of 124 cases of noise-induced hearing loss is used for evaluation. Magnitude of noise-induced hearing loss based on hearing threshold levels averaged over the frequencies 1, 2 and 3 kHz. The rationale of the method, practical application and three worked examples are developed. A simpler short-cut method is developed and shown to be equivalent to the full method in most cases. The method offers a practical approach to quantification of noise-induced hearing loss.

Predicting Hearing Thresholds in Occupational Noise-Induced Hearing Loss by Auditory Steady State Responses

Currently available behavioral tools for the assessment of noise-induced hearing loss (NIHL) depend on the reliable cooperation of the subject. Furthermore, in workers' compensation cases, there is considerable financial gain to be had from exaggerating symptoms, such that accurate assessment of true hearing threshold levels is essential. An alternative objective physiologic tool for assessing NIHL is the auditory steady state response (ASSR) test, which combines frequency specificity with a high level of auditory stimulation, making it applicable for the evaluation of subjects with a moderate to severe deficit. The primary aim of the study was to assess the value of the multifrequency ASSR test in predicting the behavioral warble-tone audiogram in a large sample of young subjects with NIHL of varying severity or with normal hearing. The secondary goal was to assess suprathreshold ASSR growth functions in these two groups. The study group included 157 subjects regularly exposed to high levels of occupational noise, who attended a university-associated audiological clinic for evaluation of NIHL from 2009 through 2011. All underwent a behavioral audiogram, and on the basis of the findings, were divided into those with NIHL (108 subjects, 216 ears) or normal hearing (49 subjects, 98 ears). The accuracy of the ASSR threshold estimations for frequencies of 500, 1000, 2000, and 4000 Hz was compared between groups, and the specificity and sensitivity of the ASSR test in differentiating ears with or without NIHL was calculated using receiver operating characteristic analysis. Linear regression analysis was used to formulate an equation to predict the behavioral warble-tone audiogram at each test frequency using ASSR thresholds. Multifrequency ASSR amplitude growth as a function of stimulus intensity was compared between the NIHL and normal-hearing groups for 1000 Hz and 4000 Hz carrier frequencies. In the subjects with NIHL, ASSR thresholds to various frequencies were significantly and highly correlated with the behavioral warble-tone thresholds; Pearson correlation coefficients ranged from 0.6 to 0.8 over the four frequencies tested. Differences between thresholds ranged from 10 to 13 dB. The configuration of the ASSR waveforms closely approximated the behavioral audiogram. The sensitivity for screening hearing thresholds was 92%; by frequency, sensitivity ranged between 92.7 and 98.4%, but specificity was lower, especially at the low frequencies. ASSR accurately predicted moderate and severe NIHL. The mean ASSR growth amplitude to increasing stimulus level for 1000 and 4000 Hz was significantly steeper in the NIHL than in the normal-hearing group, with no significant difference between frequencies. The ASSR test has a high sensitivity to detect moderate to severe hearing loss in subjects with NIHL. Its use can facilitate the early identification of noise-exposed workers with NIHL. It may also serve an important medico-legal function in cases of workers' compensation. The ASSR test is not, by itself, an appropriate tool for hearing screening in the general population.

Audiometric notch as a sign of noise induced hearing loss

OBJECTIVESTo investigate the relation between different types of exposure to noise and a classic sign of noise induced hearing loss (NIHL), the audiometric notch.METHODSThe study sample had exposure to both...

Characteristics of click-evoked otoacoustic emissions in ears with normal hearing and with noise-induced hearing loss.

The clinical application of click-evoked otoacoustic emissions (EOAE) in the assessment of noise-induced hearing loss (NIHL) was examined in a group of 72 ears with NIHL and 61 ears with normal hearing (NH). The characteristics of the EOAE in ears with NIHL significantly differed from the NH, according to all EOAE parameters tested in the present study. The mean overall EOAE level was lower and the mean EOAE nonlinearity threshold was worse in the NIHL group. In 95% of the NH ears the EOAE spectrum range was wide, while in 91.5% of the NIHL ears the range was narrow. Moreover, in 94% of the ears with NIHL, the frequency at which the hearing loss began (BHL) was at or above the frequency of the last peak in the EOAE spectrum (FLP). Furthermore, combination of EOAE spectral measures correctly discriminate on average 93.5% of ears with NH from NIHL (sensitivity) and 92% of ears with NIHL from NH (specificity). In contrast, the nonlinearity threshold and the overall level of EOAE yielded lower specificity of less than 33%. It was therefore concluded that EOAE spectrum may serve as a useful and objective tool in screening adults with suspected noise-induced high frequency hearing loss.