Excitation patterns of two auditory models applied for noise induced hearing loss assessment

Noise induced hearing loss (NIHL) as one of the major avoidable occupational related health issues has been studied for decades. To assess NIHL, the excitation pattern (EP) has been considered as one of the mechanisms to estimate the movements of the basilar membrane (BM) in the cochlea. In this study, two auditory filters, dual resonance nonlinear (DRNL) filter and rounded-exponential (ROEX) filter are applied to create two EPs, the velocity EP and the loudness EP respectively. Two noise hazard metrics are proposed based on two proposed EPs to evaluate hazardous levels caused by different types of noise. Moreover Gaussian noise and tone signals are simulated to evaluate performances of the proposed EPs and the noise metrics. The results show that both EPs can reflect the responses of the BM to different types of noise. For Gaussian noise there is a frequency shift between the velocity EP and the loudness EP. The results suggest that both EPs can be used for assessment of NIHL.

Teens at Risk: Audiologists Respond

Auditory fatigue model applications to predict noise induced hearing loss in human and chinchilla

NADH against noise-induced hearing loss: Evidence from models of "temporary" and "permanent" deafness.

Basic and applied aspects of noise-induced hearing loss: R.J. Salvi, D. Henderson, R.P. Hamernik and V. Colletti (Eds.) (Plenum, New York, 1986, 666 p., U.S. $97.50)

Existing noise metrics and modeling for noise induced hearing loss (NIHL) have limitations on prediction of gradually developing NIHL (GDHL) caused by high-level occupational noise. In this study, two auditory fatigue models have been proposed for prediction of GDHL in human. The generalized mammalian auditory model incorporating dual resonant nonlinear (DRNL) filter is used to obtain the velocity distribution on basilar membrane (BM). The velocities of BM as the input loads quantitatively reflect the mechanical fatigue failure of organ of Corti. In addition, experimental human hearing loss data are used to validate the effectiveness of the proposed auditory fatigue models. The regression analysis results show that both auditory fatigue models demonstrate high correlations with human hearing loss data.

Hearing impairment, the most prevalent sensory deficit, affects more than 466 million people worldwide (WHO). We presently lack causative treatment for the most common form, sensorineural hearing impairment; hearing aids and cochlear implants (CI) remain the only means of hearing restoration. We engaged with CI users to learn about their expectations and their willingness to collaborate with health care professionals on establishing novel therapies. We summarize upcoming CI innovations, gene therapies, and regenerative approaches and evaluate the chances for clinical translation of these novel strategies. We conclude that there remains an unmet medical need for improving hearing restoration and that we are likely to witness the clinical translation of gene therapy and major CI innovations within this decade.

Perioperative Hearing Impairment

Noise induced hearing loss (NIHL) remains as a severe health problem worldwide. Existing noise metrics and modeling for evaluation of NIHL are limited on prediction of gradually developing NIHL (GDHL) caused by high-level occupational noise. In this study, we proposed two auditory fatigue based models, including equal velocity level (EVL) and complex velocity level (CVL), which combine the high-cycle fatigue theory with the mammalian auditory model, to predict GDHL. The mammalian auditory model is introduced by combining the transfer function of the external-middle ear and the triple-path nonlinear (TRNL) filter to obtain velocities of basilar membrane (BM) in cochlea. The high-cycle fatigue theory is based on the assumption that GDHL can be considered as a process of long-cycle mechanical fatigue failure of organ of Corti. Furthermore, a series of chinchilla experimental data are used to validate the effectiveness of the proposed fatigue models. The regression analysis results show that both proposed fatigue models have high corrections with four hearing loss indices. It indicates that the proposed models can accurately predict hearing loss in chinchilla. Results suggest that the CVL model is more accurate compared to the EVL model on prediction of the auditory risk of exposure to hazardous occupational noise.

Background: Noise Induced Hearing Loss (NIHL) is used to symbolize accumulative and persistent hearing loss due to progressive exposure to high levels of noise for months or year. Design: A cross-sectional study. Setting: Al-Karama Teaching Hospital and Wasit Co. Textile Industries. Aims and objective: To specify frequency of hearing loss among workers in the knitting industry, to registration the level of the noise in the weaving department and to specify the realization about the impact of noise on the hearing. Materials and methods: From June to August 2011, the level of noise in the weaving department has been recorded. 200 workers had been sent to our hospital, interviewed according to already prepared questioner and audio logically assessed. Results and discussion: The mean level of noise at 12measurement points was 87-96dB. Which was greater than the allowable noise level for continuous 8 hours working per day? It has been established that 113 workers had NIHL, 29% of hearing loss (the greater percentage) was in the mild category (26-40dB) at high frequency (4-6KHz) group and the minimal NIHL notch within 2 kHz and 4KHz were 6% and 22% from the workers respectively. The hearing difficulty was not the most common complaints 29.4%, while ear discomfort was 55.4% and tinnitus was 43%, because NIHL usually include the high frequencies at first hence the worker can promote the NIHL and he didn't complain from loss of hearing. No one used the personal noise protective devices (PPD) and only 44 workers (24%) (P-value≤ 0.1) who considers that the noise is a hazard on health. Conclusion: Wasit Co. Textile Industries Noise measurement is greater than the allowable noise scale for 8 hours. NIHL can be developed many years before worker will complain from hearing loss.

Introduction. Noise-induced hearing loss is a rather prevalent condition and can be distressing for a substantial proportion of patients, although researches describing psychological characteristics in noise-induced occupational hearing loss patients are not numerous.The study aims to find the effects of occupational noise on the psychological status among noise-induced hearing loss (NIHL) patients.Methods. Two groups, cross-sectional design. Study sample: 44 occupational noiseinduced male forming NIHL patients group (n = 21) and a control group (n = 23). Both groups were tested using the Russian versions of psychological questionnaires.Results. Almost one third of NIHL patients are the highly anxiety individuals as compared with the healthy participants (p < 0.01). Mixed type of response to the surrounding reality combined a high need for self-actualization with high self-control, tendency to inhibit and restrain behavioral reactions, in this case it is possible to “overlap” both neurotic and behavioral responses, which can affect the general overstrain and manifest by the somatization of the internal conflict. In general, NIHL patients use constructive cognitive, emotional and behavioral coping strategies. Patients use both constructive and tense defense mechanisms. Conclusion. It has been established that in patients with NIHL, in comparison with practically healthy persons, tension accumulates, and a tendency to psychotraumatization appears. However, it is currently difficult to determine whether NIHL is a predisposing factor for these psychological characteristics, so further research is needed to determine how significant this relationship is. Key words: noise-induced hearing loss, occupational noise, psychological profile>˂ 0.01). Mixed type of response to the surrounding reality combined a high need for self-actualization with high self-control, tendency to inhibit and restrain behavioral reactions, in this case it is possible to “overlap” both neurotic and behavioral responses, which can affect the general overstrain and manifest by the somatization of the internal conflict. In general, NIHL patients use constructive cognitive, emotional and behavioral coping strategies. Patients use both constructive and tense defense mechanisms.Conclusion. It has been established that in patients with NIHL, in comparison with practically healthy persons, tension accumulates, and a tendency to psychotraumatization appears. However, it is currently difficult to determine whether NIHL is a predisposing factor for these psychological characteristics, so further research is needed to determine how significant this relationship is.

To test a kurtosis-adjusted cumulative noise exposure (CNE) metric for use in evaluating the risk of hearing loss among workers exposed to industrial noises. Specifically, to evaluate whether the kurtosis-adjusted CNE (1) provides a better association with observed industrial noise-induced hearing loss, and (2) provides a single metric applicable to both complex (non-Gaussian [non-G]) and continuous or steady state (Gaussian [G]) noise exposures for predicting noise-induced hearing loss (dose-response curves). Audiometric and noise exposure data were acquired on a population of screened workers (N = 341) from two steel manufacturing plants located in Zhejiang province and a textile manufacturing plant located in Henan province, China. All the subjects from the two steel manufacturing plants (N = 178) were exposed to complex noise, whereas the subjects from textile manufacturing plant (N = 163) were exposed to a G continuous noise. Each subject was given an otologic examination to determine their pure-tone HTL and had their personal 8-hr equivalent A-weighted noise exposure (LAeq) and full-shift noise kurtosis statistic (which is sensitive to the peaks and temporal characteristics of noise exposures) measured. For each subject, an unadjusted and kurtosis-adjusted CNE index for the years worked was created. Multiple linear regression analysis controlling for age was used to determine the relationship between CNE (unadjusted and kurtosis adjusted) and the mean HTL at 3, 4, and 6 kHz (HTL346) among the complex noise-exposed group. In addition, each subject's HTLs from 0.5 to 8.0 kHz were age and sex adjusted using Annex A (ISO-1999) to determine whether they had adjusted high-frequency noise-induced hearing loss (AHFNIHL), defined as an adjusted HTL shift of 30 dB or greater at 3.0, 4.0, or 6.0 kHz in either ear. Dose-response curves for AHFNIHL were developed separately for workers exposed to G and non-G noise using both unadjusted and adjusted CNE as the exposure matric. Multiple linear regression analysis among complex exposed workers demonstrated that the correlation between HTL3,4,6 and CNE controlling for age was improved when using the kurtosis-adjusted CNE compared with the unadjusted CNE (R = 0.386 versus 0.350) and that noise accounted for a greater proportion of hearing loss. In addition, although dose-response curves for AHFNIHL were distinctly different when using unadjusted CNE, they overlapped when using the kurtosis-adjusted CNE. For the same exposure level, the prevalence of NIHL is greater in workers exposed to complex noise environments than in workers exposed to a continuous noise. Kurtosis adjustment of CNE improved the correlation with NIHL and provided a single metric for dose-response effects across different types of noise. The kurtosis-adjusted CNE may be a reasonable candidate for use in NIHL risk assessment across a wide variety of noise environments.

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.

The Ca2+/calmodulin-dependent protein kinase kinases (CaMKKs) are serine/threonine-directed protein kinases that are activated following increases in intracellular calcium, playing a critical role in neuronal signaling. Inner-ear-trauma-induced calcium overload in sensory hair cells has been well documented in the pathogenesis of traumatic noise-induced hair cell death and hearing loss, but there are no established pharmaceutical therapies available due to a lack of specific therapeutic targets. In this study, we investigated the activation of CaMKKβ in the inner ear after traumatic noise exposure and assessed the prevention of noise-induced hearing loss (NIHL) with RNA silencing. Treatment with short hairpin RNA of CaMKKβ (shCaMKKβ) via adeno-associated virus transduction significantly knocked down CaMKKβ expression in the inner ear. Knockdown of CaMKKβ significantly attenuated noise-induced hair cell loss and hearing loss (NIHL). Additionally, pretreatment with naked CaMKKβ small interfering RNA (siCaMKKβ) attenuated noise-induced losses of inner hair cell synapses and OHCs and NIHL. Furthermore, traumatic noise exposure activates CaMKKβ in OHCs as demonstrated by immunolabeling for p-CaMKI. CaMKKβ mRNA assessed by fluorescence in-situ hybridization and immunolabeling for CaMKKβ in OHCs also increased after the exposure. Finally, pretreatment with siCaMKKβ diminished noise-induced activation of AMPKα in OHCs. These findings demonstrate that traumatic-noise-induced OHC loss and hearing loss occur primarily via activation of CaMKKβ. Targeting CaMKKβ is a key strategy for prevention of noise-induced hearing loss. Furthermore, our data suggest that noise-induced activation of AMPKα in OHCs occurs via the CaMKKβ pathway.

This paper reviews the ISO-1999 and ANSI S3.44 standards and the literature related to prediction of noise-induced hearing loss (NIHL) in humans. The dearth of contemporary population-based studies of hearing loss among industrial, low noise-exposed individuals have made the ISO-1999 and ANSI S3.44 standards a key source of comparative data for assessing the risk of NIHL. This paper will highlight how these standards have been used in several published papers to examine the magnitude of NIHL risk, predictions of noise-induced thresholds in hearing conservation data, and to generate hypotheses regarding the biologic plausibility of hearing loss due to chemicals or other ototoxic agents.