Clinical practice guidelines for the diagnosis and management of acute sensorineural hearing loss.

OBJECTIVE: Acute sensorineural hearing loss represents a spectrum of conditions characterized by sudden onset hearing loss. The "Clinical Practice Guidelines for the Diagnosis and Management of Acute Sensorineural Hearing Loss" were issued as the first clinical practice guidelines in Japan outlining the standard diagnosis and treatment. The purpose of this article is to strengthen the guidelines by adding the scientific evidence including a systematic review of the latest publications, and to widely introduce the current treatment options based on the scientific evidence. METHODS: The clinical practice guidelines were completed by 1) retrospective data analysis (using nationwide survey data), 2) systematic literature review, and 3) selected clinical questions (CQs). Additional systematic review of each disease was performed to strengthen the scientific evidence of the diagnosis and treatment in the guidelines. RESULTS: Based on the nationwide survey results and the systematic literature review summary, the standard diagnosis flowchart and treatment options, including the CQs and recommendations, were determined. CONCLUSION: The guidelines present a summary of the standard approaches for the diagnosis and treatment of acute sensorineural hearing loss. We hope that these guidelines will be used in medical practice and that they will initiate further research.

Recovery rate after acute acoustic trauma: a case series and meta-analysis.

OBJECTIVE: Steroids given systemically, locally, or both are the mainstay of treatment for acute acoustic trauma (AAT). The overall recovery rate (full, partial, and none) is undetermined. STUDY DESIGN: Original case series and systematic literature review. SETTING: Case series of a tertiary referral center and a systematic literature review. METHODS: Cases of AAT between 2012 and 2022 were retrospectively analyzed for demographics, acoustic trauma characteristics, treatment modality and delay and prognosis. This case series was added to the series identified by a systematic literature review. This review included "Medline" via "PubMed", "EMBASE", and "Google scholar". All series were pooled for meta-analysis defining prognosis following steroidal treatment for AAT patients. RESULTS: The pooled analyses included 662 ears, out of which 250 underwent complete recovery of hearing (overall proportion = 0.2809, 95%confidence interval [CI] = 0.1611-0.4178). Any recovery was recorded for 477 ears (overall proportion = 0.7185, 95% CI = 0.5671-0.8493) and no recovery was documented for 185 ears (overall proportion = 0.2815, 95% CI = 0.1507-0.4329). CONCLUSION: The rate of overall recovery for AAT is around 70%, and around 30% for full recovery when steroids are initiated within the first 2 weeks following the insult.

[Occupational diseases related to otorhinolaryngology]. / Berufskrankheiten mit Bezug zur HNO-Heilkunde.

In the German Ordinance on Occupational Diseases (BKV), there are currently 82 occupational diseases listed, of which 18 partially or completely fall within the field of ENT medicine due to the associated health disorders. Noise-induced hearing loss is usually the focus of attention for the ENT specialist, but it has long since ceased to be the only occupational disease. In order to help uncover possible causalities between occupational noxious substances and diseases, it is important that physicians report their own observations and new scientific findings regarding suspected cases to the German Social Accident Insurance, especially in situations where cancer may be linked to occupational influences.

Do Surgical Smoke Evacuators Increase the Risk of Hearing Loss for Operative Personnel During Routine Adenotonsillectomy Surgery?

INTRODUCTION: Aerosol mitigation equipment implemented due to COVID-19 has increased noise levels in the operating room (OR) during otolaryngological procedures. Intraoperative sound levels may potentially place personnel at risk for occupational hearing loss. This study hypothesized that cumulative intraoperative noise exposures with aerosol mitigation equipment exceed recommended occupational noise exposure levels. METHODS: Sound levels generated by the surgical smoke evacuator (SSE) during adenotonsillectomy were measured using a sound level meter and compared to surgery without SSE. RESULTS: Thirteen adenotonsillectomy surgeries were recorded. Mean sound levels with the SSE were greater than the control (72 ± 3 A-weighted decibels (dBA) vs. 68 ± 2 dBA; p=0.015). Maximum noise levels during surgery with SSE reached 82 ± 3 dBA. CONCLUSION: Surgeons performing adenotonsillectomy with aerosol mitigation equipment are exposed to significant noise levels. Intraoperative sound levels exceeded international standards for work requiring concentration. Innovation is needed to reduce cumulative OR noise exposures.

Comparative analysis of hearing loss caused by steady-state noise and impulse noise.

BACKGROUND: Varied noise environments, such as impulse noise and steady-state noise, may induce distinct patterns of hearing impairment among personnel exposed to prolonged noise. However, comparative studies on these effects remain limited. OBJECTIVE: This study aims to delineate the different characteristics of hearing loss in workers exposed to steady-state noise and impulse noise. METHODS: As of December 2020, 96 workers exposed to steady-state noise and 177 workers exposed to impulse noise were assessed. Hearing loss across various frequencies was measured using pure tone audiometry and distortion product otoacoustic emission (DPOAE) audiometry. RESULTS: Both groups of workers exposed to steady-state noise and impulse noise exhibited high frequencies hearing loss. The steady-state noise group displayed significantly greater hearing loss at lower frequencies in the early stages, spanning 1- 5 years of work (P < 0.05). Among individuals exposed to impulse noise for extended periods (over 10 years), the observed hearing loss surpassed that of the steady-state noise group, displaying a statistically significant difference (P < 0.05). CONCLUSION: Hearing loss resulting from both steady-state noise and impulse noise predominantly occurs at high frequencies. Early exposure to steady-state noise induces more pronounced hearing loss at speech frequencies compared to impulse noise.

Evaluation of Noise Exposure Levels in Pediatric ENT Operating Rooms.

OBJECTIVE: Operating room (OR) sounds may surpass noise exposure thresholds and induce hearing loss. Noise intensity emitted by various surgical instruments during common pediatric otolaryngologic procedures were compared at the ear-level of the surgeon and patient to evaluate the need for quality improvement measures. STUDY DESIGN: Cross-sectional study. SETTING: Single tertiary care center. METHODS: Noise levels were measured using the RISEPRO Sound Level Meter and SoundMeter X 10.0.4 at the ear level of surgeon and patient every 5 minutes. Operative procedure and instrument type were recorded. Measured noise levels were compared against ambient noise levels and the Apple Watch Noise application. RESULTS: Two hundred forty-two total occasions of noise were recorded across 62 surgical cases. Cochlear implantation surgery produces the loudest case at the ear-level of the patient (91.8 Lq Peak dB; P < .001). The otologic drill was the loudest instrument for the patient (92.1 Lq Peak dB; P < .001), while the powered microdebrider was the loudest instrument for the surgeon (90.7 Lq Peak dB; P = .036). Noise measurements between surgeon and patient were similar (P < .05). Overall agreement between the Noise application and Sound Level Meter was excellent (intraclass correlation coefficient of 0.8, with a 95% confidence interval ranging from 0.32 to 0.92). CONCLUSION: Otolaryngology OR noises can surpass normal safe thresholds. Failure to be aware of this may unwittingly expose providers to noise-related hearing loss. Mitigation strategies should be employed. Quality improvement measures, including attention to surgical instrument volume settings and periodic decibel measurements with sound applications, can promote long-term hearing conservation. DISCUSSION: Otolaryngology OR noises can surpass normal safe thresholds. Failure to be aware of this may unwittingly expose providers to noise-related hearing loss. The duration, frequency of exposure, and volume levels of noise should be studied further. IMPLICATIONS FOR PRACTICE: Mitigation strategies should be employed. Quality improvement measures, including attention to surgical instrument volume settings and periodic decibel measurements with sound applications, can promote long-term hearing conservation.

The Current State of Proteomics and Metabolomics for Inner Ear Health and Disease.

Characterising inner ear disorders represents a significant challenge due to a lack of reliable experimental procedures and identified biomarkers. It is also difficult to access the complex microenvironments of the inner ear and investigate specific pathological indicators through conventional techniques. Omics technologies have the potential to play a vital role in revolutionising the diagnosis of ear disorders by providing a comprehensive understanding of biological systems at various molecular levels. These approaches reveal valuable information about biomolecular signatures within the cochlear tissue or fluids such as the perilymphatic and endolymphatic fluid. Proteomics identifies changes in protein abundance, while metabolomics explores metabolic products and pathways, aiding the characterisation and early diagnosis of diseases. Although there are different methods for identifying and quantifying biomolecules, mass spectrometry, as part of proteomics and metabolomics analysis, could be utilised as an effective instrument for understanding different inner ear disorders. This study aims to review the literature on the application of proteomic and metabolomic approaches by specifically focusing on Meniere's disease, ototoxicity, noise-induced hearing loss, and vestibular schwannoma. Determining potential protein and metabolite biomarkers may be helpful for the diagnosis and treatment of inner ear problems.

Advancing noise management in aviation: Strategic approaches for preventing noise-induced hearing loss.

As urbanization and population growth escalate, the challenge of noise pollution intensifies, particularly within the aviation industry. This review examines current insights into noise-induced hearing loss (NIHL) in aviation, highlighting the risks to pilots, cabin crew, aircraft maintenance engineers, and ground staff from continuous exposure to high-level noise. It evaluates existing noise management and hearing conservation strategies, identifying key obstacles and exploring new technological solutions. While progress in developing protective devices and noise control technologies is evident, gaps in their widespread implementation persist. The study underscores the need for an integrated strategy combining regulatory compliance, technological advances, and targeted educational efforts. It advocates for global collaboration and policy development to safeguard the auditory health of aviation workers and proposes a strategic framework to enhance hearing conservation practices within the unique challenges of the aviation sector.

Modeling correlated uncertainties in stochastic compartmental models.

We consider compartmental models of communicable disease with uncertain contact rates. Stochastic fluctuations are often added to the contact rate to account for uncertainties. White noise, which is the typical choice for the fluctuations, leads to significant underestimation of the disease severity. Here, starting from reasonable assumptions on the social behavior of individuals, we model the contacts as a Markov process which takes into account the temporal correlations present in human social activities. Consequently, we show that the mean-reverting Ornstein-Uhlenbeck (OU) process is the correct model for the stochastic contact rate. We demonstrate the implication of our model on two examples: a Susceptibles-Infected-Susceptibles (SIS) model and a Susceptibles-Exposed-Infected-Removed (SEIR) model of the COVID-19 pandemic and compare the results to the available US data from the Johns Hopkins University database. In particular, we observe that both compartmental models with white noise uncertainties undergo transitions that lead to the systematic underestimation of the spread of the disease. In contrast, modeling the contact rate with the OU process significantly hinders such unrealistic noise-induced transitions. For the SIS model, we derive its stationary probability density analytically, for both white and correlated noise. This allows us to give a complete description of the model's asymptotic behavior as a function of its bifurcation parameters, i.e., the basic reproduction number, noise intensity, and correlation time. For the SEIR model, where the probability density is not available in closed form, we study the transitions using Monte Carlo simulations. Our modeling approach can be used to quantify uncertain parameters in a broad range of biological systems.

ABCC1 deficiency potentiated noise-induced hearing loss in mice by impairing cochlear antioxidant capacity.

The ABCC1 gene belongs to the ATP-binding cassette membrane transporter superfamily, which plays a crucial role in the efflux of various endogenous and exogenous substances. Mutations in ABCC1 can result in autosomal dominant hearing loss. However, the specific roles of ABCC1 in auditory function are not fully understood. Through immunofluorescence, we found that ABCC1 was expressed in microvascular endothelial cells (ECs) of the stria vascularis (StV) in the murine cochlea. Then, an Abcc1 knockout mouse model was established by using CRISPR/Cas9 technology to elucidate the role of ABCC1 in the inner ear. The ABR threshold did not significantly differ between WT and Abcc1-/- mice at any age studied. After noise exposure, the ABR thresholds of the WT and Abcc1-/- mice were significantly elevated. Interestingly, after 14 days of noise exposure, ABR thresholds largely returned to pre-exposure levels in WT mice but not in Abcc1-/- mice. Our subsequent experiments showed that microvascular integrity in the StV was compromised and that the number of outer hair cells and the number of ribbons were significantly decreased in the cochleae of Abcc1-/- mice post-exposure. Besides, the production of ROS and the accumulation of 4-HNE significantly increased. Furthermore, StV microvascular ECs were cultured to elucidate the role of ABCC1 in these cells under glucose oxidase challenge. Notably, 30 U/L glucose oxidase (GO) induced severe oxidative stress damage in Abcc1-/- cells. Compared with WT cells, the ROS and 4-HNE levels and the apoptotic rate were significantly elevated in Abcc1-/- cells. In addition, the reduced GSH/GSSG ratio was significantly decreased in Abcc1-/- cells after GO treatment. Taken together, Abcc1-/- mice are more susceptible to noise-induced hearing loss, possibly because ABCC1 knockdown compromises the GSH antioxidant system of StV ECs. The exogenous antioxidant N-acetylcysteine (NAC) may protect against oxidative damage in Abcc1-/- murine cochleae and ECs.

FDA-Approved MEK1/2 Inhibitor, Trametinib, Protects Mice from Cisplatin and Noise-Induced Hearing Loss.

Hearing loss is one of the most common types of disability; however, there is only one FDA-approved drug to prevent any type of hearing loss. Treatment with the highly effective chemotherapy agent, cisplatin, and exposure to high decibel noises are two of the most common causes of hearing loss. The mitogen activated protein kinase (MAPK) pathway, a phosphorylation cascade consisting of RAF, MEK1/2, and ERK1/2, has been implicated in both types of hearing loss. Pharmacologically inhibiting BRAF or ERK1/2 is protective from noise and cisplatin-induced hearing loss in multiple mouse models. Trametinib, a MEK1/2 inhibitor, protects from cisplatin induced outer hair cell death in mouse cochlear explants; however, to the best of our knowledge, inhibiting MEK1/2 has not yet been shown to be protective from hearing loss in vivo. In this study, we demonstrate that trametinib protects from cisplatin-induced hearing loss in a translationally relevant mouse model and does not interfere with cisplatin's tumor killing efficacy in cancer cell lines. Higher doses of trametinib were toxic to mice when combined with cisplatin but lower doses of the drug were protective from hearing loss without any known toxicity. Trametinib also protected mice from noise-induced hearing loss and synaptic damage. This study shows that MEK1/2 inhibition protects from both insults of hearing loss and that targeting all three kinases in the MAPK pathway protect from cisplatin and noise-induced hearing loss in mice.

ERK1/2 Inhibition via the Oral Administration of Tizaterkib Alleviates Noise-Induced Hearing Loss While Tempering down the Immune Response.

Noise-induced hearing loss (NIHL) is a major cause of hearing impairment and is linked to dementia and mental health conditions, yet no FDA-approved drugs exist to prevent it. Downregulating the mitogen-activated protein kinase (MAPK) cellular pathway has emerged as a promising approach to attenuate NIHL, but the molecular targets and the mechanism of protection are not fully understood. Here, we tested specifically the role of the kinases ERK1/2 in noise otoprotection using a newly developed, highly specific ERK1/2 inhibitor, tizaterkib, in preclinical animal models. Tizaterkib is currently being tested in phase 1 clinical trials for cancer treatment and has high oral bioavailability and low predicted systemic toxicity in mice and humans. In this study, we performed dose-response measurements of tizaterkib's efficacy against permanent NIHL in adult FVB/NJ mice, and its minimum effective dose (0.5 mg/kg/bw), therapeutic index (>50), and window of opportunity (<48 h) were determined. The drug, administered orally twice daily for 3 days, 24 h after 2 h of 100 dB or 106 dB SPL noise exposure, at a dose equivalent to what is prescribed currently for humans in clinical trials, conferred an average protection of 20-25 dB SPL in both female and male mice. The drug shielded mice from the noise-induced synaptic damage which occurs following loud noise exposure. Equally interesting, tizaterkib was shown to decrease the number of CD45- and CD68-positive immune cells in the mouse cochlea following noise exposure. This study suggests that repurposing tizaterkib and the ERK1/2 kinases' inhibition could be a promising strategy for the treatment of NIHL.

Trametinib, a MEK1/2 Inhibitor, Protects Mice from Cisplatin- and Noise-Induced Hearing Loss.

Hearing loss is one of the most common types of disability; however, there is only one FDA-approved drug to prevent any type of hearing loss. Treatment with the highly effective chemotherapy agent, cisplatin, and exposure to high-decibel noises are two of the most common causes of hearing loss. The mitogen-activated protein kinase (MAPK) pathway, a phosphorylation cascade consisting of RAF, MEK1/2, and ERK1/2, has been implicated in both types of hearing loss. Pharmacologically inhibiting BRAF or ERK1/2 is protective against noise- and cisplatin-induced hearing loss in multiple mouse models. Trametinib, a MEK1/2 inhibitor, protects from cisplatin-induced outer hair cell death in mouse cochlear explants; however, to the best of our knowledge, inhibiting MEK1/2 has not yet been shown to be protective against hearing loss in vivo. In this study, we demonstrate that trametinib protects against cisplatin-induced hearing loss in a translationally relevant mouse model and does not interfere with cisplatin's tumor-killing efficacy in cancer cell lines. Higher doses of trametinib were toxic to mice when combined with cisplatin, but lower doses of the drug were protective against hearing loss without any known toxicity. Trametinib also protected mice from noise-induced hearing loss and synaptic damage. This study shows that MEK1/2 inhibition protects against both insults of hearing loss, as well as that targeting all three kinases in the MAPK pathway protects mice from cisplatin- and noise-induced hearing loss.

Transient Receptor Potential (TRP) Channels in Cochlear Function: Looking Beyond Mechanotransduction.

Transient receptor potential (TRP) channels play key roles in sensory biology as transducers of various stimuli. Although these ion channels are expressed in the cochlea, their functions remain poorly understood. Recent studies by Vélez-Ortega and colleagues indicate that their expression by non-sensory supporting cells helps limit damage from acoustic trauma.

Early Loss of Spiral Ganglion Neurons in the Auditory System after Noise Trauma.

INTRODUCTION: Noise-induced hearing loss is one of the most frequent recognized occupational diseases. The time course of the involved pathologies is still under investigation. Several studies have demonstrated an acute damage of the sensory tissue, but only few experiments investigated the degeneration of (type I) spiral ganglion neurons (SGNs), representing the primary neurons in the auditory system. The aim of the present study was to investigate the time course of SGN degeneration within a 7-day period after traumatic noise exposure starting immediately after trauma. METHODS: Young adult normal hearing mice were noise exposed for 3 h with a broadband noise (5-20 kHz) at 115 dB SPL. Auditory threshold shift was measured by auditory brainstem recordings, and SGN densities were analyzed at different time points during the first week after acoustic trauma. RESULTS: Significant reduction of SGN densities was detected and is accompanied by a significant hearing loss. Degeneration starts within hours after the applied trauma, further progressing within days post-exposure. DISCUSSION: Early neurodegeneration in the auditory periphery seems to be induced by direct overstimulation of the auditory nerve fibers. SGN loss is supposed to be a result of inflammatory responses and neural deprivation, leading to permanent hearing loss and auditory processing deficits.

Examining the utility of near infrared light as pre-exposure therapy to mitigate temporary noise-induced hearing loss in humans.

Introduction: This study sought to determine the effect of Occupational Safety and Health Administration (OSHA) compliant noise on auditory health and assess whether pre-noise near infrared (NIR) light therapy can mitigate the effects of noise exposure. Methods: Over four visits, participants (n = 30, NCT#: 03834714) with normal hearing completed baseline hearing health assessments followed by exposure to open ear, continuous pink noise at 94 dBA for 15 min. Immediately thereafter, post-noise hearing tests at 3000, 4000, and 6000 Hz and distortion product otoacoustic emissions (DPOAEs) were conducted along with the Modified Rhyme Test (MRT), Masking Level Difference Test (MLD), and Fixed Level Frequency Tests (FLFT) [collectively referred to as the Central and Peripheral Auditory Test Battery (CPATB)] to acquire baseline noise sensitivity profiles. Participants were then randomized to either Active or Sham NIR light therapy for 30 min binaurally to conclude Visit 1. Visit 2 (≥24 and ≤ 48 h from Visit 1) began with an additional 30-min session of Active NIR light therapy or Sham followed by repeat CPATB testing and noise exposure. Post-noise testing was again conducted immediately after noise exposure to assess the effect of NIR light therapy. The remaining visits were conducted following ≥2 weeks of noise rest in a cross-over design (i.e., those who had received Active NIR light therapy in Visits 1 and 2 received Sham therapy in Visits 3 and 4). Results: Recovery hearing tests and DPOAEs were completed at the end of each visit. Participants experienced temporary threshold shifts (TTS) immediately following noise exposure, with a mean shift of 6.79 dB HL (±6.25), 10.61 dB HL (±6.89), and 7.30 dB HL (±7.25) at 3000, 4000, and 6000 Hz, respectively, though all thresholds returned to baseline at 3000, 4000, and 6000 Hz within 75 min of noise exposure. Paradoxically, Active NIR light therapy threshold shifts were statistically higher than Sham therapy at 3000 Hz (p = 0.04), but no other differences were observed at the other frequencies tested. An age sub-analysis demonstrated that TTS among younger adults were generally larger in the Sham therapy group versus Active therapy, though this was not statistically different. There were no differences in CPATB test results across Active or Sham groups. Finally, we observed no changes in auditory function or central processing following noise exposure, suggestive of healthy and resilient inner ears. Conclusion: In this study, locally administered NIR prior to noise exposure did not induce a significant protective effect in mitigating noise-induced TTS. Further exploration is needed to implement effective dosage and administration for this promising otoprotective therapy.

Recreational music exposure and hearing health in young adults.

OBJECTIVE: This study aimed to compare daily and total recreational music exposure levels and extended-spectrum audiogram results in young adults without pre-existing hearing problems. DESIGN: The study included healthy volunteers aged 18-25 with no known ear disease or hearing loss. Participants completed a questionnaire, underwent otoscopic and tympanometric examinations, and determined preferred music volumes in an audiometry booth using calibrated music samples of their preferred genres. Hearing thresholds up to 16 kiloHertz (kHz) were measured. Daily music exposure for each participant was normalized to 8 h to calculate a time-weighted average of 8 h (TWA8). Total exposure (TE) was calculated by multiplying TWA8 by the number of years of music listening. RESULTS: A total of 32.4% of participants had TWA8s above 65 dB. Their hearing thresholds at 125, 250, 500, and 16,000 Hz and the average of 125 Hz-8 kHz were significantly higher. Participants with TWA8s above 65 dB were also more prone to speaking loudly and experiencing communication difficulties on the phone. Those with a TE of more than 400 experienced significantly more speech discrimination difficulty in noisy environments and temporary hearing loss/tinnitus after exposure to loud music. Participants with a TE above 700 had worse thresholds at 4, 14, and 16 kHz frequencies, as well as 125-8000 Hz and 500-4000 Hz averages compared to those with a TE below 700. CONCLUSIONS: This study provides evidence that recreational music with much lower exposure levels than the universally accepted TWA8 of 85 dB could negatively impact hearing in healthy young adults. Therefore, maintaining a maximum TWA8 of 65 dB is recommended.

Prevalence and associated factors of noise-induced hearing loss among workers in Bishoftu Central Air Base of Ethiopia.

Excessive occupational exposure to noise results in a well-recognized occupational hearing loss which is prevalent in many workplaces and now it is taken as a global problem. Therefore, this study aims to assess the prevalence of noise-induced hearing loss and associated factors among workers in the Bishoftu Central Air Base in Ethiopia. An institutional-based cross-sectional study was conducted among 260 central air base workers through face-to-face interviews, an environment noise survey, and an audiometric test for data collection. Data were entered by Epi-data version 3.1 and SPSS was used to analyze the data. Finally, a statistical analysis such as descriptive and binary logistic regression analysis was applied. A P-value < 0.05 at 95% CI was considered statistically significant. The overall prevalence of noise-induced hearing loss and hearing impairments was 24.6 and 30.9%, respectively. The highest prevalence of noise-induced hearing loss was recorded for workers who were exposed to noise levels greater than 90 dBA. Out of 132 workers exposed to the average noise level of 75 dB A, only 5% of workers were affected with noise-induced hearing loss, while 128 workers exposed to an average noise level equal to or greater than 90 dB A, 19.6% of workers were identified with noise-induced hearing loss. Regarding sex, around 21.9% of male workers were identified with noise-induced hearing loss. Workers who were exposed to a high noise level workplace previously or before the Central Air Base workplace were five times (AOR = 5.0, 95% CI 1.74-14.36) more likely affected by noise-induced hearing loss than those workers not previously exposed. Those workers who were exposed to greater or equal to 90dBA noise level were 4.98 times (AOR = 4.98, 95% CI 2.59-9.58) more likely to be exposed to noise-induced levels than those who were exposed to less than 90dBA noise level. Moreover, male air base workers were 3.5 times more likely exposed to hearing impairment than female workers (AOR = 3.5, 95% CI 1.01-12.0). This study identified that the prevalence of noise-induced hearing loss and hearing impairments was significantly high. So implementation of a hearing conservation program, giving noise education, and supplying adequate hearing protective devices (HPDs) are essentials.

Quantification of suppressor effects on breech and action noise from AR-15 pattern firearms and its implications for the protection of human hearing.

Noise from firearms is well known to be harmful to human hearing. This problem has been addressed by various military units through the use of muzzle suppressors. However, as suppressor technology has advanced, shooters report hearing the mechanical action of gas-operated semi-automatic rifles (ArmaLite Rifle Model 15 style aka AR-15) as being louder than the suppressed muzzle noise. This study aims to evaluate if harmful noise is present in the shooter's ear, even when impulse noise emanating from the muzzle is suppressed. To characterize the impulse noise of the firearm action caused by the reciprocation of the bolt carrier group (BCG) and subsequent impact when it returns to battery (the forward locked position), the muzzle of a rifle was placed through a constructed plywood wall, and the noise of the action/breech was measured independently from the muzzle noise. This research finds that the impact of the BCG returning to battery (132 dBZ) has the potential to be harmful to the shooter's hearing even when the noise from the muzzle is effectively suppressed.

Development of an artificial intelligence based occupational noise induced hearing loss early warning system for mine workers.

Introduction: Occupational Noise Induced Hearing Loss (ONIHL) is one of the most prevalent conditions among mine workers globally. This reality is due to mine workers being exposed to noise produced by heavy machinery, rock drilling, blasting, and so on. This condition can be compounded by the fact that mine workers often work in confined workspaces for extended periods of time, where little to no attenuation of noise occurs. The objective of this research work is to present a preliminary study of the development of a hearing loss, early monitoring system for mine workers. Methodology: The system consists of a smart watch and smart hearing muff equipped with sound sensors which collect noise intensity levels and the frequency of exposure. The collected information is transferred to a database where machine learning algorithms namely the logistic regression, support vector machines, decision tree and Random Forest Classifier are used to classify and cluster it into levels of priority. Feedback is then sent from the database to a mine worker smart watch based on priority level. In cases where the priority level is extreme, indicating high levels of noise, the smart watch vibrates to alert the miner. The developed system was tested in a mock mine environment consisting of a 67 metres tunnel located in the basement of a building whose roof top represents the "surface" of a mine. The mock-mine shape, size of the tunnel, steel-support infrastructure, and ventilation system are analogous to deep hard-rock mine. The wireless channel propagation of the mock-mine is statistically characterized in 2.4-2.5 GHz frequency band. Actual underground mine material was used to build the mock mine to ensure it mimics a real mine as close as possible. The system was tested by 50 participants both male and female ranging from ages of 18 to 60 years. Results and discussion: Preliminary results of the system show decision tree had the highest accuracy compared to the other algorithms used. It has an average testing accuracy of 91.25% and average training accuracy of 99.79%. The system also showed a good response level in terms of detection of noise input levels of exposure, transmission of the information to the data base and communication of recommendations to the miner. The developed system is still undergoing further refinements and testing prior to being tested in an actual mine.