Hearing threshold shifts among military pilots of the Israeli Air Force

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.

Frequency-Following Response (FFR) in Military Pilots

Introduction  Good hearing in pilots, including central auditory skills, is critical for flight safety and the prevention of aircraft accidents. Pure tone audiometry alone may not be enough to assess hearing in the members of this population who, in addition to high noise levels, routinely face speech recognition tasks in non-ideal conditions.

Objective  To characterize the frequency-following response (FFR) of a group of military pilots compared with a control group.

Methods  Twenty military pilots in the Study Group and 20 non-pilot military personnel, not exposed to noise in their work, in the Control Group, all with normal hearing, aged between 30 and 40 years old, completed a questionnaire to assess their hearing habits, and their FFRs were measured with a /da/ syllable (duration 40 milliseconds, speed 10.9/s), at 80 dB NA in the right ear. All procedures were approved by the ethical committee of the institution. Statistical analysis was performed using the t-Student or Mann-Whitney tests for quantitative variables, and the Fisher or chi-squared tests for qualitative variables, and a value of p  < 0.05 was considered to be statistically significant.

Results  There was no significant difference between the groups regarding auditory habits. In the FFR, wave amplitudes A ( p  = 0.01) and C ( p  = 0.04) were significantly lower in the Study Group.

Conclusion  Working as a military pilot can be a crucial factor in determining an individual's typical FFR pattern, demonstrated in the present study by statistically significant reductions in the amplitudes of the A and C waves.

Masking level difference among brazilian military personnel: a comparison between pilots and non-pilots

OBJECTIVES

The aims of this study were to investigate auditory habits and binaural interaction among pilot and non-pilot military personnel from the Brazilian Air Force.

DESIGN

A cross-sectional study using (1) an auditory habits questionnaire to outline the groups auditory profile and (2) the masking level difference test (MLD, Auditec, Saint Louis®) to evaluate and compare the groups.

STUDY SAMPLE

Forty military male personnel aged between 30-40 years old, all with normal hearing, comprising 20 pilots in the study group (SG), and 20 non-pilots, not exposed to noise, in the control group (CG).

RESULTS

There was no significant difference between groups regarding auditory habits. In the MLD test, a significantly better performance under the homophasic condition (S0N0) was found in the SG. Under the antiphasic condition (SπN0) there were no differences between groups. This combination resulted in a significantly lower MLD in the SG compared to the CG.

CONCLUSIONS

Repeated exposure to conditions where active pilots have to learn to recognise speech in noisy backgrounds may lead to a better performance in the MLD's homophasic condition (S0N0).

The Immediate and Long-Term Impact of Military Aircraft Noise on Hearing: A Cross-Sectional Comparison of Fighter Pilots and Ground Staff

We examined the immediate and long-term impacts of military aircraft noise exposure on noise-induced hearing loss (NIHL) in fighter pilots and ground staff. We recruited 40 pilots, 40 ground staff, and 136 age-matched controls; all participants underwent hearing tests, including conventional pure-tone audiometry (PTA) (0.25–8.0 kHz), extended high-frequency (EHF) audiometry (9.0–18.0 kHz), and distortion-product otoacoustic emission (DPOAE) as a recent reference. A subsequent hearing test immediately after flight-mission noise exposure was requested. The results revealed higher recent hearing thresholds in pilots and ground staff than in controls. Threshold shifts at many octave band frequencies were also significantly elevated in ground staff. The grouped frequency threshold was significantly elevated in the 4–8 kHz high-frequency range. After a single flight-mission noise exposure, both ground staff and pilots showed decreased signal-to-noise ratios for DPOAE (1–8 kHz), whereas only ground staff showed significantly elevated left-ear hearing thresholds at 3, 11.2, and 12.5 kHz by conventional and EHF PTA. Fighter pilots and ground staff serve in hazardous noise-exposed environments that cause hearing damage and subsequent NIHL, but ground staff may be more vulnerable. A comprehensive hearing conservation program should be implemented to protect high-risk service members, and especially ground staff, from high-intensity noise exposure.

Noise-induced hearing loss in the military dental setting: a UK legislative perspective

INTRODUCTION

Health professionals working in the dental environment are potentially at risk of noise-induced hearing loss (NIHL) due to the use of clinical and laboratory equipment. Workplaces engaging in the practice of dentistry within the UK are subject to legislation from the Control of Noise at Work (CNW) regulations 2005. Clinicians working in the military are at further increased risk of NIHL due to exposure from additional risk factors such as rifles or aircraft engines. To our knowledge, no authors have previously studied the noise levels experienced in a military dental setting or compared noise levels in a typical dental practice with current UK legislation.

METHOD

Measurements of noise levels experienced by a dentist, dental nurse and dental hygienist during a standard conservation procedure were assessed using wearable noise dose-badges. Furthermore, noise levels within a dental technician's work space were also assessed. Noise levels produced by representative clinical and laboratory equipment were assessed and compared with CNW legislation.

RESULTS

The highest level for clinical equipment was produced by the suction apparatus while aspirating up a cup of water at 76 dB. For laboratory equipment, the lower exposure action value (LEAV) of 80 dB would be exceeded in 2.1 hours' use of the trimmer, 3.6 hours' use of the vibrating table and 9 min use of the airline.

CONCLUSIONS

Noise levels experienced by clinicians within the dental surgery were well below the legislative LEAV thresholds for both peak and continuous noise. However, noise levels produced by laboratory equipment were far higher and there is clearly the potential for excessive noise exposure for dental professional in the everyday setting. Dental professionals responsible for dental laboratory settings must be familiar with the CNW regulations and measures put in place that control the inadvertent breach of legislation. Hearing protection must be mandated when using equipment that exceeds the LEAV and an educational programme is required to explain both their correct use and the rationale behind it. Methods of mitigating that risk further require exploration such as alternative methods of completing the tasks performed by the airline or reducing the noise generated by it, such as by reducing the supply pressure or using an alternative nozzle design.