Field Attenuation of Foam Earplugs

Reliability of an extended version of the 3m™ Eargage tool to assess earcanal size and assist earplug selection

OBJECTIVE

Evaluate the ability of an extended version of the 3 MTM Eargage to estimate the earcanal size and assess the likelihood that a particular earplug can fit an individual's earcanal, ultimately serving as a tool for selecting earplugs in the field.

DESIGN

Earcanal morphology, assessed through earcanal earmolds scans, is compared to earcanal size assessed with the extended eargage (EE) via box plots and Pearson linear correlations coefficients. Relations between attenuation measured on participants (for 6 different earplugs) and their earcanal size assessed with the EE are established via comparison tests.

STUDY SAMPLE

121 participants exposed to occupational noise (103 men, 18 women, mean age 47 years).

RESULTS

The earcanal size assessed with the EE allows for estimating the area of the earcanal's first bend cross-section (correlation coefficient   r = 0.533, p < 0.001). Extremely large earcanals (12.7% of earcanals in our sample) lead to significantly lower earplug attenuation (potentially inadequate) than smaller earcanals.

CONCLUSIONS

The EE is a simple and inexpensive tool easily deployable in the field to assist earplugs selection. When extended with sizes larger than the maximum size of the commercial tool, it allows for detecting individuals with extremely large earcanals who are most likely to be under-protected.

Hearing protection field attenuation estimation systems and associated training for reducing workers' exposure to noise

BACKGROUND

Global Burden of Disease studies identify hearing loss as the third leading cause of years lived with a disability. Their estimates point to large societal and individual costs from unaddressed hearing difficulties. Workplace noise is an important modifiable risk factor; if addressed, it could significantly reduce the global burden of disease. In practice, providing hearing protection devices (HPDs) is the most common intervention to reduce noise exposure at work. However, lack of fit of HPDs, especially earplugs, can greatly limit their effectiveness. This may be the case for 40% of users. Testing the fit and providing instructions to improve noise attenuation might be effective. In the past two decades, hearing protection fit-test systems have been developed and evaluated in the field. They are called field attenuation estimation systems. They measure the noise attenuation obtained by individual workers using HPDs. If there is a lack of fit, instruction for better fit is provided, and may lead to better noise attenuation obtained by HPDs.

OBJECTIVES

To assess: (1) the effects of field attenuation estimation systems and associated training on the noise attenuation obtained by HPDs compared to no instruction or to less instruction in workers exposed to noise; and (2) whether these interventions promote adherence to HPD use.

SEARCH METHODS

We used CENTRAL, MEDLINE, five other databases, and two trial registers, together with reference checking, citation searching, and contact with study authors to identify studies. We imposed no language or date restrictions. The latest search date was February 2024.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), cluster-RCTs, controlled before-after studies (CBAs), and interrupted time-series studies (ITSs) exploring HPD fit testing in workers exposed to noise levels of more than 80 A-weighted decibels (or dBA) who use hearing protection devices. The unit 'dBA' reports on the use of a frequency-weighting filter to adjust sound measurement results to better reflect how human ears process sound. The outcome noise attenuation had to be measured either as a personal attenuation rating (PAR), PAR pass rate, or both. PAR pass rate is the percentage of workers who passed a pre-established level of sufficient attenuation from their HPDs, identified on the basis of their individual noise exposure.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, risk of bias, and extracted data. We categorised interventions as fit testing of HPDs with instructions at different levels (no instructions, simple instructions, and extensive instructions).

MAIN RESULTS

We included three RCTs (756 participants). We did not find any studies that examined whether fit testing and training contributed to hearing protector use, nor any studies that examined whether age, gender, or HPD experience influenced attenuation. We would have included any adverse effects if mentioned by the trial authors, but none reported them. None of the included studies blinded participants; two studies blinded those who delivered the intervention. Effects of fit testing of HPDs with instructions (simple or extensive) versus fit testing of HPDs without instructions Testing the fit of foam and premoulded earplugs accompanied by simple instructions probably does not improve their noise attenuation in the short term after the test (1-month follow-up: mean difference (MD) 1.62 decibels (dB), 95% confidence interval (CI) -0.93 to 4.17; 1 study, 209 participants; 4-month follow-up: MD 0.40 dB, 95% CI -2.28 to 3.08; 1 study, 197 participants; both moderate-certainty evidence). The intervention probably does not improve noise attenuation in the long term (MD 0.15 dB, 95% CI -3.44 to 3.74; 1 study, 103 participants; moderate-certainty evidence). Fit testing of premoulded earplugs with extensive instructions on the fit of the earplugs may improve their noise attenuation at the immediate retest when compared to fit testing without instructions (MD 8.34 dB, 95% CI 7.32 to 9.36; 1 study, 100 participants; low-certainty evidence). Effects of fit testing of HPDs with extensive instructions versus fit testing of HPDs with simple instructions Fit testing of foam earplugs with extensive instructions probably improves their attenuation (MD 8.62 dB, 95% CI 6.31 to 10.93; 1 study, 321 participants; moderate-certainty evidence) and also the pass rate of sufficient attenuation (risk ratio (RR) 1.75, 95% CI 1.44 to 2.11; 1 study, 321 participants; moderate-certainty evidence) when compared to fit testing with simple instructions immediately after the test. This is significant because every 3 dB decrease in noise exposure level halves the sound energy entering the ear. No RCTs reported on the long-term effectiveness of the HPD fit testing with extensive instructions.

AUTHORS' CONCLUSIONS

HPD fit testing accompanied by simple instructions probably does not improve noise attenuation from foam and premoulded earplugs. Testing the fit of foam and premoulded earplugs with extensive instructions probably improves attenuation and PAR pass rate immediately after the test. The effects of fit testing associated with training to improve attenuation may vary with types of HPDs and training methods. Better-designed trials with larger sample sizes are required to increase the certainty of the evidence.

A Systematic Literature Review of the Factors Influencing Hearing Protection Device Usage among Industrial Workers

This systematic literature review (SLR) aims to determine the factors influencing the use of hearing protection devices (HPDs) among industrial workers. This study was guided by the PRISMA Statement (Preferred Reporting Items for Systematic reviews and Meta-Analyses) review method, and four databases comprising Scopus, Science Direct, PubMed, Wiley Online Library, and Google Scholar were employed. A total of 196 articles were identified, and 28 studies on the factors associated with HPD use among industrial workers from 2006 to 2021 met the inclusion criteria. Resultantly, five main themes emerged from this review: sociodemographic (29%), interpersonal influences (18%), situational influences (18%), cognitive-perceptual (29%), and health-promoting behavior (6%) associated with HPD use among industrial workers. A total of 17 sub-themes were identified, including age, gender, educational level, noise level, working experience, social models, interpersonal support, social norms, safety climate, training, organizational support, perceived barrier, perceived susceptibility, perceived severity, perceived benefit, self-efficacy, and cues to action. The significant factors influencing workers to use HPDs are sociodemographic, interpersonal influences, situational influences, and health-promoting behavior. Future studies should focus on the cues to action toward human behavior influencing the use of HPDs, workers' health status, and comorbidities of hearing loss. Therefore, this systematic study gives valuable reference resources for up-and-coming researchers as well as new knowledge to expert professionals and academics in various industries.

Effect of Hearing Protection Use on Pianists’ Performance and Experience: Comparing Foam and Musician Earplugs

Professional musicians are often exposed to high noise levels and thus face the risk of noise-induced hearing loss. Yet, adoption rates for hearing protection among musicians are low. Previous surveys indicate that the chief concern is the effect of hearing protection use on performance. However, few studies have investigated actual changes in performance when wearing hearing protection. We report an experiment investigating differences in pianists’ performance and experience with and without hearing protection. We compare the effect of foam earplugs and musician earplugs, designed to preserve sound quality with a flat frequency response. The analysis revealed that participants performed overall more loudly with the foam earplugs than with the musician earplugs, and in turn performances with the musician earplugs were louder than the open condition, indicating a compensatory effect. However, this effect was stronger for novel excerpts than for familiar excerpts. No effect was observed on dynamic range. Furthermore, we observed an acclimatization effect, whereby the effect of hearing protection use, observed on the first performance, decreased on the second performance. In terms of experience, participants reported changes in coloration, difficulties gauging dynamics and articulation, and increased effort required when performing with hearing protection. These effects were more pronounced when wearing the foam earplugs, and the participants reported finding the musician earplugs more comfortable to wear and play with. In conclusion, hearing protection use affects pianists’ performance particularly in terms of dynamics and their experience more so in terms of coloration. But the effects are less marked for familiar pieces and after repetition, suggesting that pianists can quickly adjust their playing when playing familiar pieces with hearing protection.

A deep neural-network classifier for photograph-based estimation of hearing protection attenuation and fit

Occupational and recreational acoustic noise exposure is known to cause permanent hearing damage and reduced quality of life, which indicates the importance of noise controls including hearing protection devices (HPDs) in situations where high noise levels exist. While HPDs can provide adequate protection for many noise exposures, it is often a challenge to properly train HPD users and maintain compliance with usage guidelines. HPD fit-testing systems are commercially available to ensure proper attenuation is achieved, but they often require specific facilities designed for hearing testing (e.g., a quiet room or an audiometric booth) or special equipment (e.g., modified HPDs designed specifically for fit testing). In this study, we explored using visual information from a photograph of an HPD inserted into the ear to estimate hearing protector attenuation. Our dataset consists of 960 unique photographs from four types of hearing protectors across 160 individuals. We achieved 73% classification accuracy in predicting if the fit was greater or less than the median measured attenuation (29 dB at 1 kHz) using a deep neural network. Ultimately, the fit-test technique developed in this research could be used for training as well as for automated compliance monitoring in noisy environments to prevent hearing loss.