Evidence-Based Occupational Hearing Screening I: Modeling the Effects of Real-World Noise Environments on the Likelihood of Effective Speech Communication

A Critique of the National Academies of Sciences, Engineering, and Medicine Report (2021) and the Diagnostic Accuracy of Measurements of Functional Hearing Ability

PURPOSE

The Social Security Administration (SSA) asked the National Academies of Sciences, Engineering, and Medicine (NASEM, 2021) to make recommendations for tests of functional hearing ability. These tests include speech perception measures administered in quiet and in background noise. Such tests are required to make disability determinations for adults and children following cochlear implantation. The test review required an evaluation of the diagnostic accuracy of the speech perception measures. Following a review of the literature, NASEM wrote that the evidence needed to support such a recommendation was lacking. They resorted to "professional judgment" and recommended a monosyllabic word recognition test, presumably in quiet, along with a measure of self-report or parent report. The primary purpose of this article was to critically review the committee's report. The secondary purpose was to critique the committee's recommendation of a monosyllabic word test as a measure of functional hearing ability for disability determinations. The third purpose was to provide a review of diagnostic accuracy studies not included in NASEM (2021) with an emphasis on speech recognition in noise (SRN) tests.

CONCLUSIONS

In contrast to the committee's recommendation, studies have shown that a monosyllabic word test is a poor predictor of SRN ability. Contrary to the conclusion of NASEM (2021), diagnostic accuracy studies have been conducted for a few SRN tests. The Hearing in Noise Test and the AzBio SRN test have published data demonstrating their ability to correctly identify the presence and absence of an SRN disorder.

Speech-in-noise testing: Innovative applications for pediatric patients, underrepresented populations, fitness for duty, clinical trials, and remote services

Speech perception testing, defined as providing standardized speech stimuli and requiring a listener to provide a behavioral and scored response, has been an integral part of the audiologic test battery since the beginning of the audiology profession. Over the past several decades, limitations in the diagnostic and prognostic validity of standard speech perception testing as routinely administered in the clinic have been noted, and the promotion of speech-in-noise testing has been highlighted. This review will summarize emerging and innovative approaches to speech-in-noise testing with a focus on five applications: (1) pediatric considerations promoting the measurement of sensory and cognitive components separately; (2) appropriately serving underrepresented populations with special attention to racial, ethnic, and linguistic minorities, as well as considering biological sex and/or gender differences as variables of interest; (3) binaural fitness for duty assessments of functional hearing for occupational settings that demand the ability to detect, recognize, and localize sounds; (4) utilization of speech-in-noise tests in pharmacotherapeutic clinical trials with considerations to the drug mechanistic action, the patient populations, and the study design; and (5) online and mobile applications of hearing assessment that increase accessibility and the direct-to-consumer market.

The effect of hearing protection worn by talker and/or target listener on speech production in quiet and noise

Speech production while wearing hearing protectors poses significant challenges due to their occlusion effect and disruption of the Lombard effect. An experiment was conducted with 24 individuals as they read a list of 12 sentences in open ears and while wearing an earmuff in quiet and in four different noises [pink, International Female Fluctuating Masker (IFFM), speech-spectrum noise (SSnoise), and helicopter] at two levels (70 and 85 dBA). An acoustic manikin, fitted or not with an identical protector, served as the target listener. In noise, speech levels decreased when the talkers wore the earmuff but increased when the target listener was fitted with the earmuff. When the earmuff was used by both the talkers and target listener, speech levels were lower by 3-6 dB at the higher noise level compared to when they were both open ears. Speech levels were typically lower, but extended speech intelligibility index estimates were consistently higher, in fluctuating (IFFM, helicopter) than in continuous noises (pink, SSnoise). Talkers' pitch frequency and voice spectrum measurements followed very closely the changes in speech levels, showing no evidence of compensatory voice modifications. Implications of the lower talker speech levels when wearing hearing protectors are discussed in terms of protector selection, training, and individuals with hearing loss.

Respiration mask waveguide optimisation for maximised speech intelligibility

Both the scarcity and environmental impact of disposable face masks, as in the COVID-19 pandemic, have instigated the recent development of reusable masks. Such face masks reduce transmission of infectious agents and particulates, but often impact a user's ability to be understood when materials, such as silicone or hard polymers, are used. In this work, we present a numerical optimisation approach to optimise waveguide topology, where a waveguide is used to transmit and direct sound from the interior of the mask volume to the outside air. This approach allows acoustic energy to be maximised according to specific frequency bands, including those most relevant to human speech. We employ this method to convert a resuscitator mask, made of silicone, into respiration personal protective equipment (PPE) that maximises the speech intelligibility index (SII). We validate this approach experimentally as well, showing improved SII when using the fabricated device. Together, this design represents a unique and effective approach to utilize and adapt available apparatus to filter air while improving the ability to communicate effectively, including in healthcare settings.

The Effect of Hearing-Protection Devices on Auditory Situational Awareness and Listening Effort

OBJECTIVES

Hearing-protection devices (HPDs) are made available, and often are required, for industrial use as well as military training exercises and operational duties. However, these devices often are disliked, and consequently not worn, in part because they compromise situational awareness through reduced sound detection and localization performance as well as degraded speech intelligibility. In this study, we carried out a series of tests, involving normal-hearing subjects and multiple background-noise conditions, designed to evaluate the performance of four HPDs in terms of their modifications of auditory-detection thresholds, sound-localization accuracy, and speech intelligibility. In addition, we assessed their impact on listening effort to understand how the additional effort required to perceive and process auditory signals while wearing an HPD reduces available cognitive resources for other tasks.

DESIGN

Thirteen normal-hearing subjects participated in a protocol, which included auditory tasks designed to measure detection and localization performance, speech intelligibility, and cognitive load. Each participant repeated the battery of tests with unoccluded ears and four hearing protectors, two active (electronic) and two passive. The tasks were performed both in quiet and in background noise.

RESULTS

Our findings indicate that, in variable degrees, all of the tested HPDs induce performance degradation on most of the conducted tasks as compared to the open ear. Of particular note in this study is the finding of increased cognitive load or listening effort, as measured by visual reaction time, for some hearing protectors during a dual-task, which added working-memory demands to the speech-intelligibility task.

CONCLUSIONS

These results indicate that situational awareness can vary greatly across the spectrum of HPDs, and that listening effort is another aspect of performance that should be considered in future studies. The increased listening effort induced by hearing protectors may lead to earlier cognitive fatigue in noisy environments. Further study is required to characterize how auditory performance is limited by the combination of hearing impairment and the use of HPDs, and how the effects of such limitations can be linked to safe and effective use of hearing protection to maximize job performance.

Minimal and Mild Hearing Loss in Children: Association with Auditory Perception, Cognition, and Communication Problems

OBJECTIVES

"Minimal" and "mild" hearing loss are the most common but least understood forms of hearing loss in children. Children with better ear hearing level as low as 30 dB HL have a global language impairment and, according to the World Health Organization, a "disabling level of hearing loss." We examined in a population of 6- to 11-year-olds how hearing level ≤40.0 dB HL (1 and 4 kHz pure-tone average, PTA, threshold) is related to auditory perception, cognition, and communication.

DESIGN

School children (n = 1638) were recruited in 4 centers across the United Kingdom. They completed a battery of hearing (audiometry, filter width, temporal envelope, speech-in-noise) and cognitive (IQ, attention, verbal memory, receptive language, reading) tests. Caregivers assessed their children's communication and listening skills. Children included in this study (702 male; 752 female) had 4 reliable tone thresholds (1, 4 kHz each ear), and no caregiver reported medical or intellectual disorder. Normal-hearing children (n = 1124, 77.1%) had all 4 thresholds and PTA <15 dB HL. Children with ≥15 dB HL for at least 1 threshold, and PTA <20 dB (n = 245, 16.8%) had minimal hearing loss. Children with 20 ≤PTA <40 dB HL (n = 88, 6.0%) had mild hearing loss. Interaural asymmetric hearing loss ( left PTA - right PTA ≥10 dB) was found in 28.9% of those with minimal and 39.8% of those with mild hearing loss.

RESULTS

Speech perception in noise, indexed by vowel-consonant-vowel pseudoword repetition in speech-modulated noise, was impaired in children with minimal and mild hearing loss, relative to normal-hearing children. Effect size was largest (d = 0.63) in asymmetric mild hearing loss and smallest (d = 0.21) in symmetric minimal hearing loss. Spectral (filter width) and temporal (backward masking) perceptions were impaired in children with both forms of hearing loss, but suprathreshold perception generally related only weakly to PTA. Speech-in-noise (nonsense syllables) and language (pseudoword repetition) were also impaired in both forms of hearing loss and correlated more strongly with PTA. Children with mild hearing loss were additionally impaired in working memory (digit span) and reading, and generally performed more poorly than those with minimal loss. Asymmetric hearing loss produced as much impairment overall on both auditory and cognitive tasks as symmetric hearing loss. Nonverbal IQ, attention, and caregiver-rated listening and communication were not significantly impaired in children with hearing loss. Modeling suggested that 15 dB HL is objectively an appropriate lower audibility limit for diagnosis of hearing loss.

CONCLUSIONS

Hearing loss between 15 and 30 dB PTA is, at ~20%, much more prevalent in 6- to 11-year-old children than most current estimates. Key aspects of auditory and cognitive skills are impaired in both symmetric and asymmetric minimal and mild hearing loss. Hearing loss <30 dB HL is most closely related to speech perception in noise, and to cognitive abilities underpinning language and reading. The results suggest wider use of speech-in-noise measures to diagnose and assess management of hearing loss and reduction of the clinical hearing loss threshold for children to 15 dB HL.

Audibility-Based Hearing Aid Fitting Criteria for Children With Mild Bilateral Hearing Loss

Purpose Because of uncertainty about the level of hearing where hearing aids should be provided to children, the goal of the current study was to develop audibility-based hearing aid candidacy criteria based on the relationship between unaided hearing and language outcomes in a group of children with hearing loss who did not wear hearing aids. Method Unaided hearing and language outcomes were examined for 52 children with mild-to-severe hearing losses. A group of 52 children with typical hearing matched for age, nonverbal intelligence, and socioeconomic status was included as a comparison group representing the range of optimal language outcomes. Two audibility-based criteria were considered: (a) the level of unaided hearing where unaided children with hearing loss fell below the median for children with typical hearing and (b) the level of unaided hearing where the slope of language outcomes changed significantly based on an iterative, piecewise regression modeling approach. Results The level of unaided audibility for children with hearing loss that was associated with differences in language development from children with typical hearing or based on the modeling approach varied across outcomes and criteria but converged at an unaided speech intelligibility index of 80. Conclusions Children with hearing loss who have unaided speech intelligibility index values less than 80 may be at risk for delays in language development without hearing aids. The unaided speech intelligibility index potentially could be used as a clinical criterion for hearing aid fitting candidacy for children with hearing loss.

Beyond the audiogram: application of models of auditory fitness for duty to assess communication in the real world

This manuscript provides a Commentary on a paper published in the current issue of the International Journal of Audiology and the companion paper published in Ear and Hearing by Soli et al. These papers report background, rationale and results of a novel modelling approach to assess "auditory fitness for duty," or an individual's ability to perform hearing-critical tasks related to their job, based on their likelihood of effective speech communication in the listening environment in which the task is performed.

Development of hearing standards for Ontario's Constable Selection System

Objective: Develop valid and defensible hearing standards for Ontario constables to ensure safe and efficient operations. Design: Research involved three steps: (1) identification of hearing critical (HC) tasks, (2) characterisation of real-world noise environments where these tasks are performed (3) and establishment of screening criteria and protocols for determining fitness for duty. Study sample: Three panels of subject matter experts (SMEs) from different Ontario police services participated in Steps 1 and 3. Result: Fifty-one HC tasks conducted in 25 different environments were identified. Acceptable levels of speech communication in noise were based on environments with the highest frequency, importance and difficulty ratings. The ability to understand soft speech was also deemed critical. These translated into a 2 dB maximum elevation in the Noise Composite speech recognition threshold (SRT) with the Hearing-In-Noise-Test and a threshold in quiet of 35 dBA or better. Conclusions: Speech communication modelling methodology greatly facilitates the task of developing fitness for duty hearing standards, but participation of SMEs is crucial for face validity.

Beyond the Audiogram: Application of Models of Auditory Fitness for Duty to Assess Communication in the Real World

This manuscript provides a Commentary on a paper published in the current issue of Ear and Hearing and the companion paper published in the International Journal of Audiology (Soli et al. 2018a, 2018b). These papers report background, rationale, and results of a novel modeling approach to assess "auditory fitness for duty" or an individual's ability to perform hearing-critical tasks related to their job, based on their likelihood of effective speech communication in the listening environment in which the task is performed.