Reference equivalent threshold sound pressure levels for the Wireless Automated Hearing Test System

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.

Assessment of Central Auditory Processing in Children Using a Novel Tablet-Based Platform: Application for Low- and Middle-Income Countries

OBJECTIVE

Evaluate whether a portable, tablet-based central auditory processing (CAP) test system using native language training videos and administered by minimally trained community health workers can produce CAP results comparable to previously published norms. Our secondary aim was to determine subject parameters that influence test results.

STUDY DESIGN

Cross-sectional study.

SETTING

Community-based settings in Chontales, Nicaragua, New Hampshire, and Florida.

PATIENTS

English- and/or Spanish-speaking children and adolescents (n = 245; average age, 12.20 yr; range, 6-18 yr).

MAIN OUTCOME MEASURES

Completion of the following tests with responses comparable to published norms: Pure-tone average (PTA), gap detection threshold (GDT), fixed-level frequency threshold, masking level difference (MLD), Hearing in Noise Test (HINT), Dichotic Digits Test (DDT), and Frequency Pattern Recognition (FPR) test.

RESULTS

GDT, HINT, and DDT had comparable results to previously published normative values. MLD and FPR results differed compared with previously published normative values. Most CAP tests (MLD, GDT, HINT) results were independent of age and PTA (p = 0.1-0.9). However, DDT was associated with age and PTA (p < 0.0001).

CONCLUSIONS

Pediatric CAP testing can be successfully completed in remote low- and middle- income country environments using a tablet-based platform without the presence of an audiologist. Performance on DDT improved with age but deteriorated with hearing loss. Further investigation is warranted to assess the variability of FPR.

Increasing Hearing Readiness Using Boothless Audiometry

INTRODUCTION

U.S. Army regulations require all soldiers to undergo annual audiometric testing to maintain hearing readiness. The standard method of monitoring hearing in the DoD is via multi-person testing in sound-treated booths using the Defense Occupational and Environmental Health Readiness System-Hearing Conservation. COVID-19 significantly hindered the standard method, resulting in alarming declines in hearing readiness. In response, the Army Hearing Program initiated a pilot program to use boothless audiometers to supplement standard methods to increase hearing readiness.

MATERIALS AND METHODS

Funding from the Coronavirus Aid, Relief, and Economic Security Act was used to purchase 169 boothless audiometers and increase staffing at dozens of Army Hearing Program clinics. Standard operating procedures were established for audiometric testing outside the booth using a process matching standard test parameters (i.e., test frequencies, tone characteristics, and interstimulus intervals). Additional capabilities developed to leverage this new technology during the annual hearing exam include the administration of automated contralateral masking, enhanced tinnitus screening, and hearing health education and training.

RESULTS

Monitoring audiometry using boothless audiometers has been conducted for nearly 12,000 service members worldwide. Thresholds obtained via boothless audiometers are comparable to follow-up thresholds obtained from the standard test methods in the booth (mean difference 95% CI, -1.2, 0.9), and hearing readiness has returned to pre-pandemic levels at installations where this novel technology is being used regularly.

CONCLUSIONS

Significant reductions in patient encounters as a direct result of the COVID-19 pandemic have led to innovative solutions leveraging boothless audiometers. While this has aided the primary mission to maintain a medically ready force, innovations from this endeavor highlight several additional improvements relative to current standards of care that should be considered for permanent inclusion in DoD Hearing Conservation Programs.

Extended High-Frequency Audiometry using the Wireless Automated Hearing Test System Compared to Manual Audiometry in Children and Adolescents

Objectives

Reliable wireless automated audiometry that includes extended high frequencies (EHF) outside a sound booth would increase access to monitoring programs for individuals at risk for hearing loss, particularly those at risk for ototoxicity. The purpose of the study was to compare thresholds obtained with 1) standard manual audiometry to automated thresholds measured with the Wireless Automated Hearing Test System (WAHTS) inside a sound booth, and 2) automated audiometry in the sound booth to automated audiometry outside the sound booth in an office environment.

Design

Cross-sectional, repeated measures study. Twenty-eight typically developing children and adolescents (mean = 14.6 yrs; range = 10 to 18 yrs). Audiometric thresholds were measured from 0.25 to 16 kHz with manual audiometry in the sound booth, automated audiometry in the sound booth, and automated audiometry in a typical office environment in counterbalanced order. Ambient noise levels were measured inside the sound booth and the office environment were compared to thresholds at each test frequency.

Results

Automated thresholds were overall about 5 dB better compared to manual thresholds, with greater differences in the extended high frequency range (EHF;10-16 kHz). The majority of automated thresholds measured in a quiet office were within ± 10 dB of automated thresholds measured in a sound booth (84%), while only 56% of automated thresholds in the sound booth were within ± 10 dB of manual thresholds. No relationship was found between automated thresholds measured in the office environment and the average or maximum ambient noise level.

Conclusions

These results indicate that self-administered, automated audiometry results in slightly better thresholds overall than manually administered audiometry in children, consistent with previous studies in adults. Ambient noise levels in a typical office environment did not have an adverse effect on audiometric thresholds measured using noise attenuation headphones. Thresholds measured using an automated tablet with noise attenuating headphones could improve access to hearing assessment for children with a variety of risk factors. Additional studies of extended high frequency automated audiometry in a wider age range are needed to establish normative thresholds.

Noise-induced hearing disorders: Clinical and investigational tools

A series of articles discussing advanced diagnostics that can be used to assess noise injury and associated noise-induced hearing disorders (NIHD) was developed under the umbrella of the United States Department of Defense Hearing Center of Excellence Pharmaceutical Interventions for Hearing Loss working group. The overarching goals of the current series were to provide insight into (1) well-established and more recently developed metrics that are sensitive for detection of cochlear pathology or diagnosis of NIHD, and (2) the tools that are available for characterizing individual noise hazard as personal exposure will vary based on distance to the sound source and placement of hearing protection devices. In addition to discussing the utility of advanced diagnostics in patient care settings, the current articles discuss the selection of outcomes and end points that can be considered for use in clinical trials investigating hearing loss prevention and hearing rehabilitation.

Boothless audiometry: Ambient noise considerations

Ambient noise in the test environment will impact signal detection during hearing threshold measurements due to psychoacoustic masking effects. Technical standards specify the maximum permissible ambient noise levels (MPANLs) for use during audiometric testing. MPANLs are dependent on several factors, including transducer characteristics (supra-aural, circumaural, type of ear cushions or earphone enclosures, and insert earphones), the nature of the hearing test being performed (air conduction vs bone conduction and threshold test vs screen at a suprathreshold level), and measurement instrumentation. The nature of the ambient noise (spectrum and constant vs variable) at the test site must be determined and continually accounted for during the boothless hearing test procedure. Ambient noise monitoring procedures are reviewed and examples of ambient noise characteristics in real-world settings, where hearing testing might be performed outside of a sound-treated environment, are provided. Practical considerations are presented, including examples of available tools for ambient noise monitoring, selection of test locations, and transducer attenuation. These are discussed in the context of calculating MPANLs and how best to ensure that ambient noise levels are not negatively impacting the validity of hearing thresholds.