Extended high-frequency audiometry in research and clinical practice

Investigating the role of extended high-frequency audibility on temporal envelope processing and spatial release from masking

Extended high-frequency (EHF) hearing loss offers a model for investigating the onset of auditory dysfunction before changes in standard audiometric thresholds occur. However, the impact on auditory perception remains poorly understood. This study evaluated the relationship between EHF hearing sensitivity and monaural and binaural measures of auditory temporal resolution and spatial release from masking in young adults (aged 20-35 years) with normal hearing thresholds in the clinical frequency range (.25 - 8 kHz) with varying degrees of hearing sensitivity in the EHFs (10 - 16 kHz). Despite considerable individual variability in performance on perceptual tasks, no significant correlations were found between EHF thresholds and measures of temporal processing or speech perception. This suggests that certain aspects of auditory processing within the standard audiometric frequency range may remain unaffected in individuals with EHF hearing loss.

Early identification of potential occupational noise-induced hearing loss: a systematic review

OBJECTIVE

This systematic review addressed two questions: 1) For which audiometric test frequencies or pure tone averages are hearing threshold levels (HTLs) most susceptible to early occupational noise induced hearing loss (NIHL) before significant damage? 2) Which early flag metric best detects early hearing shifts due to noise for occupational NIHL surveillance?

DESIGN

Systematic searches were conducted in Ovid MEDLINE(R) and Embase from July 2021 to May 2024. Eligibility was screened by two independent reviewers using Covidence. HTL results were analysed for susceptibility to noise-induced changes, and sensitivity and specificity of early flag metrics were assessed.

STUDY SAMPLE

Of 175 studies retrieved, 18 met the inclusion criteria.

RESULTS

Ten studies emphasised the importance of testing at frequencies above 8 kHz, with HTLs at 12, 14, and 16 kHz frequently identified as the most noise susceptible. Conventional frequencies of 3-6 kHz were also noted as susceptible. NIOSH and OSHA metrics had low sensitivity and specificity, but modifications improved their performance to 100% sensitivity and 98% specificity.

CONCLUSION

The review highlights the need to refine current metrics and explore extended high frequencies for NIHL monitoring. Research is required to determine frequencies for warning metrics and sensitive metrics for early occupational NIHL detection.

Association of Occupational Noise Exposure and Extended High-Frequency Hearing Loss in Young Workers With Normal Hearing

OBJECTIVES

Studies on the relationship between occupational noise exposure and extended high-frequency (EHF) hearing loss are limited. This study investigated the relationship between occupational noise exposure and EHF hearing loss in workers exposed to noise as measured by sound pressure level, exposure duration, and kurtosis to help provide a basis for early detection and prevention of hearing loss in noise-exposed workers.

DESIGN

A cross-sectional survey was conducted among 602 participants with 472 noise-exposed workers and 130 non-noise-exposed controls. General demographic characteristics, noise exposure data, and hearing thresholds at conventional frequencies (0.25 to 8 kHz) and EHF (9 to 16 kHz) were collected and analyzed. Linear mixed-effects model analyses between hearing thresholds of EHF and noise exposure indicators including the 8-h equivalent continuous A-weighted sound pressure level ( LAeq,8h ), cumulative noise exposure (CNE), and kurtosis-adjusted CNE (CNE-K) were conducted.

RESULTS

Among the 602 participants included in the analysis, 472 individuals (78.4%) were occupationally exposed to noise exposures ≥75 dBA. Significant differences ( p < 0.05) were observed in sex, exposure duration, LAeq,8h , CNE, and CNE-K between the noise-exposed group and the nonexposed group. The mean hearing thresholds for all tested extended high frequencies ranging from 9 to 16 kHz were significantly higher in the noise-exposed group than in the nonexposed group ( p < 0.05). The mean hearing thresholds of subjects in different groups of LAeq,8h exposures were generally stable with little variance in the conventional frequencies (0.25 to 8 kHz) but differed in the EHF range. Moreover, EHF hearing loss appeared to be most prominent in the subjects exposed to noise with 80 dBA < LAeq,8h ≤ 85 dBA. After the combination of the sound pressure level, exposure duration, and kurtosis by using the noise exposure indicators CNE and CNE-K, the subjects at the different noise exposures showed significant differences in hearing thresholds at EHF ( p < 0.05). Linear mixed-effected model analyses showed that the CNE-K was the best to indicate noise-induced hearing loss among the three noise exposure indicators at EHF.

CONCLUSIONS

The results indicate that the EHF hearing threshold testing is more sensitive to identifying early occupational noise-induced hearing loss than conventional audiometry. The CNE-K, an indicator combining noise energy, exposure duration, and kurtosis, is a more comprehensive and effective method for assessing the risk of EHF hearing loss due to occupational noise exposure.

How Do Enriched Speech Acoustics Support Language Acquisition in Children With Hearing Loss? A Narrative Review

Language outcomes of children with hearing loss remain heterogeneous despite recent advances in treatment and intervention. Consonants with high frequency, in particular, continue to pose challenges to affected children's speech perception and production. In this review, the authors evaluate findings of how enriched child-directed speech and song might function as a form of early family-centered intervention to remedy the effects of hearing loss on consonant acquisition already during infancy. First, they review the developmental trajectory of consonant acquisition and how it is impeded by permanent pediatric hearing loss. Second, they assess how phonetic-prosodic and lexico-structural features of caregiver speech and song could facilitate acquisition of consonants in the high-frequency range. Last, recommendations for clinical routines and further research are expressed.

A Simple Nomogram for Predicting Extended High-Frequency Hearing Loss in Pilots Despite Normal Audiometry: A Retrospective Study

BACKGROUND

The extended high-frequency (EHF; 0.9-16 kHz) region is sensitive to noise exposure and can indicate early noise-induced hearing loss. EHF hearing loss (EHFHL; >20 dB HL for EHF averages) may affect pilots' noise perception, impacting communication and response in flight. Early identification and monitoring of EHFHL are crucial for pilots' hearing health and flight safety. However, EHF is not included in routine medical assessments for pilots in China. This study aimed to develop a nomogram to predict EHFHL in pilots with normal audiograms (≤20 dB HL at each standard frequency), providing an early intervention tool.

METHODS

A total of 1091 pilots were randomly assigned to the training set (763) and validation set (328). Set characteristics were compared using univariate analysis. In the training set, least absolute shrinkage and selection operator regression identified key predictors, followed by multivariable binary logistic regression to construct a nomogram. The nomogram's performance was evaluated in both sets, assessing calibration, discrimination and clinical utility.

RESULTS

The nomogram incorporated four factors as follows: left-ear high-frequency audiometry threshold averages (HFAs: 3, 4, 6 and 8 kHz; odds ratio [OR] = 1.144; 95% confidence interval [CI] = 1.083-1.210), right-ear HFAs (OR = 1.186, 95% CI = 1.115-1.263), flight time (OR = 1.001, 95% CI = 1-1.001) and triglyceride (OR = 1.393, 95% CI = 1.038-1.885). The model's area under the curve was 0.819 (95% CI = 0.790-0.850) and 0.771 (95% CI = 0.712-0.830) during validation. The predictive model was well calibrated (Hosmer-Lemeshow test, χ2  =  10.77; P = 0.292). Decision curve analysis showed a net benefit for the training set between 4% and 88%, with similar benefits observed for the validation set from 12% to 100%.

CONCLUSION

This study developed and validated the first prediction model for EHFHL in Chinese pilots, demonstrating its reliability and clinical utility. The findings support early detection and personalised monitoring, with potential applications in hearing protection strategies and flight safety.

Extended high-frequency hearing and suprathreshold neural synchrony in the auditory brainstem

Elevated hearing thresholds in the extended high frequencies (EHFs) (>8 kHz) are often associated with poorer speech-in-noise recognition despite a clinically normal audiogram. However, whether EHF hearing loss is associated with disruptions in neural processing within the auditory brainstem remains uncertain. The objective of the present study was to investigate whether elevated EHF thresholds influence neural processing at lower frequencies in individuals with normal audiograms. Auditory brainstem responses (ABRs) were recorded at a suprathreshold level (80 dB normal hearing level) from 45 participants with clinically normal hearing. The recording protocol was optimized to obtain robust wave I of the ABR. Results revealed no significant relationship between the pure tone average for EHFs and any ABR metrics at either rate, while adjusting for the effects of age, sex, and hearing thresholds at standard frequencies (0.25-8 kHz). Rate-dependent significant sex effects for wave I and V amplitude, I-V amplitude ratio, and III and V latency were observed. Elevated EHF hearing thresholds do not significantly affect the brainstem processing in the lower frequencies (<8 kHz).

The relationship between distortion product otoacoustic emissions and audiometric thresholds in the extended high-frequency range

Distortion product otoacoustic emissions (DPOAEs) and behavioral audiometry are routinely used for hearing screening and assessment. These measures provide related information about hearing status as both are sensitive to cochlear pathologies. However, DPOAE testing is quicker and does not require a behavioral response. Despite these practical advantages, DPOAE testing is often limited to screening only low- and mid-frequencies. Variation in ear canal acoustics across ears and probe placements has resulted in less reliable measurements of DPOAEs near 4 kHz and above where standing waves commonly occur. Stimulus calibration in forward pressure level and responses in emitted pressure level can reduce measurement variability. Using these calibrations, this study assessed the correlation between audiometry and DPOAEs in the extended high frequencies where stimulus calibrations and responses are most susceptible to the effect of standing waves. Behavioral thresholds and DPOAE amplitudes were negatively correlated, and DPOAE amplitudes in emitted pressure level accounted for twice as much variance as amplitudes in conventional sound pressure level units. Both measures were correlated with age. These data show that extended high-frequency DPOAEs are sensitive to differences in audiometric thresholds and highlight the need to consider calibration techniques in clinical and research applications of DPOAEs.

An Anechoic, High-Fidelity, Multidirectional Speech Corpus

INTRODUCTION

We currently lack speech testing materials faithful to broader aspects of real-world auditory scenes such as speech directivity and extended high frequency (EHF; > 8 kHz) content that have demonstrable effects on speech perception. Here, we describe the development of a multidirectional, high-fidelity speech corpus using multichannel anechoic recordings that can be used for future studies of speech perception in complex environments by diverse listeners.

DESIGN

Fifteen male and 15 female talkers (21.3-60.5 years) recorded Bamford-Kowal-Bench (BKB) Standard Sentence Test lists, digits 0-10, and a 2.5-min unscripted narrative. Recordings were made in an anechoic chamber with 17 free-field condenser microphones spanning 0°-180° azimuth angle around the talker using a 48 kHz sampling rate.

RESULTS

Recordings resulted in a large corpus containing four BKB lists, 10 digits, and narratives produced by 30 talkers, and an additional 17 BKB lists (21 total) produced by a subset of six talkers.

CONCLUSIONS

The goal of this study was to create an anechoic, high-fidelity, multidirectional speech corpus using standard speech materials. More naturalistic narratives, useful for the creation of babble noise and speech maskers, were also recorded. A large group of 30 talkers permits testers to select speech materials based on talker characteristics relevant to a specific task. The resulting speech corpus allows for more diverse and precise speech recognition testing, including testing effects of speech directivity and EHF content. Recordings are publicly available.

Is Noise Exposure Associated With Impaired Extended High Frequency Hearing Despite a Normal Audiogram? A Systematic Review and Meta-Analysis

Understanding the initial signature of noise-induced auditory damage remains a significant priority. Animal models suggest the cochlear base is particularly vulnerable to noise, raising the possibility that early-stage noise exposure could be linked to basal cochlear dysfunction, even when thresholds at 0.25-8 kHz are normal. To investigate this in humans, we conducted a meta-analysis following a systematic review, examining the association between noise exposure and hearing in frequencies from 9 to 20 kHz as a marker for basal cochlear dysfunction. Systematic review and meta-analysis followed PRISMA guidelines and the PICOS framework. Studies on noise exposure and hearing in the 9 to 20 kHz region in adults with clinically normal audiograms were included by searching five electronic databases (e.g., PubMed). Cohorts from 30 studies, comprising approximately 2,500 participants, were systematically reviewed. Meta-analysis was conducted on 23 studies using a random-effects model for occupational and recreational noise exposure. Analysis showed a significant positive association between occupational noise and hearing thresholds, with medium effect sizes at 9 and 11.2 kHz and large effect sizes at 10, 12, 14, and 16 kHz. However, the association with recreational noise was less consistent, with significant effects only at 12, 12.5, and 16 kHz. Egger's test indicated some publication bias, specifically at 10 kHz. Findings suggest thresholds above 8 kHz may indicate early noise exposure effects, even when lower-frequency (≤8 kHz) thresholds remain normal. Longitudinal studies incorporating noise dosimetry are crucial to establish causality and further support the clinical utility of extended high-frequency testing.

Normative Data of Extended High Frequency Audiometry in Normal Hearing Subjects with Different Aged Groups

Background/Objectives: Conventional audiometry assesses hearing in the frequency range of 250-8000 Hz, while humans can detect sounds from 20 to 20,000 Hz. Hearing sensitivity above 8000 Hz can be assessed through "Extended high-frequency audiometry (EHFA)", which is useful for early detection and monitoring of hearing loss and counseling for tinnitus patients. Despite its usefulness, age significantly affects hearing sensitivity. Currently, there are no standard hearing thresholds in the EHF range categorized by age groups in Thailand. In this study, the aim was to determine normative EHFA data across different age groups in a healthy Thai population. Methods: This study included 134 participants aged 18-70 years, categorized into five age groups. All participants had normal hearing thresholds and type A tympanograms bilaterally. Following this, EHFA measurement was performed. Results: Across all age groups, there was an observed increase in median hearing thresholds as age increased. In comparison, no significant difference in median hearing thresholds was found between individuals aged 18-30 and >30-40 years. However, those over 40 years had significantly higher median thresholds across all frequencies compared to those under 40 years (p < 0.05). Based on these findings, we propose two new subgroups of 18-40 years and >40-70 years. Median hearing thresholds for those aged 18-40 was ≤20 dB HL across most frequencies, except at 16,000 Hz (30 dB HL). In the >40-70 age group, thresholds ranged from 20 dB HL at 9000 Hz to 70 dB HL at 14,000 and 16,000 Hz. However, no significant differences were found in hearing thresholds between sexes and ear sides. Conclusions: In this study, normative EHFA data were established for healthy Thai adults, appropriately divided into two groups (18-40 and >40-70 years) for clinical use. Further studies with more participants per age group are also needed to validate the results.

Trajectories of Hearing From Childhood to Adulthood

OBJECTIVES

The Dunedin Multidisciplinary Health and Development Study provides a unique opportunity to document the progression of ear health and hearing ability within the same cohort of individuals from birth. This investigation draws on hearing data from 5 to 13 years and again at 45 years of age, to explore the associations between childhood hearing variables and hearing and listening ability at age 45.

DESIGN

Multiple linear regression analyses were used to assess associations between childhood hearing (otological status and mid-frequency pure-tone average) and (a) age 45 peripheral hearing ability (mid-frequency pure-tone average and high-frequency pure-tone average), and (b) age 45 listening ability (listening in spatialized noise and subjective questionnaire on listening experiences). Sex, childhood socioeconomic status, and adult IQ were included in the model as covariates.

RESULTS

Peripheral hearing and listening abilities at age 45 were consistently associated with childhood hearing acuity at mid-frequencies. Otological status was a moderate predicting factor for high-frequency hearing and utilization of spatial listening cues in adulthood.

CONCLUSIONS

We aim to use these findings to develop a foundational model of hearing trajectories. This will form the basis for identifying precursors, to be investigated in a subsequent series of analyses, that may protect against or exacerbate hearing-associated cognitive decline in the Dunedin Study cohort as they progress from mid-life to older age.

Extended High-Frequency Thresholds: Associations With Demographic and Risk Factors, Cognitive Ability, and Hearing Outcomes in Middle-Aged and Older Adults

OBJECTIVES

This study had two objectives: to examine associations between extended high-frequency (EHF) thresholds, demographic factors (age, sex, race/ethnicity), risk factors (cardiovascular, smoking, noise exposure, occupation), and cognitive abilities; and to determine variance explained by EHF thresholds for speech perception in noise, self-rated workload/effort, and self-reported hearing difficulties.

DESIGN

This study was a retrospective analysis of a data set from the MUSC Longitudinal Cohort Study of Age-related Hearing Loss. Data from 347 middle-aged adults (45 to 64 years) and 694 older adults (≥ 65 years) were analyzed for this study. Speech perception was quantified using low-context Speech Perception In Noise (SPIN) sentences. Self-rated workload/effort was measured using the effort prompt from the National Aeronautics and Space Administration-Task Load Index. Self-reported hearing difficulty was assessed using the Hearing Handicap Inventory for the Elderly/Adults. The Wisconsin Card Sorting Task and the Stroop Neuropsychological Screening Test were used to assess selected cognitive abilities. Pure-tone averages representing conventional and EHF thresholds between 9 and 12 kHz (PTA (9 - 12 kHz) ) were utilized in simple linear regression analyses to examine relationships between thresholds and demographic and risk factors or in linear regression models to assess the contributions of PTA (9 - 12 kHz) to the variance among the three outcomes of interest. Further analyses were performed on a subset of individuals with thresholds ≤ 25 dB HL at all conventional frequencies to control for the influence of hearing loss on the association between PTA (9 - 12 kHz) and outcome measures.

RESULTS

PTA (9 - 12 kHz) was higher in males than females, and was higher in White participants than in racial Minority participants. Linear regression models showed the associations between cardiovascular risk factors and PTA (9 - 12 kHz) were not statistically significant. Older adults who reported a history of noise exposure had higher PTA (9 - 12 kHz) than those without a history, while associations between noise history and PTA (9 - 12 kHz) did not reach statistical significance for middle-aged participants. Linear models adjusting for age, sex, race and noise history showed that higher PTA (9 - 12 kHz) was associated with greater self-perceived hearing difficulty and poorer speech recognition scores in noise for both middle-aged and older participants. Workload/effort was significantly related to PTA (9 - 12 kHz) for middle-aged, but not older, participants, while cognitive task performance was correlated with PTA (9 - 12 kHz) only for older participants. In general, PTA (9 - 12 kHz) did not account for additional variance in outcome measures as compared to conventional pure-tone thresholds, with the exception of self-reported hearing difficulties in older participants. Linear models adjusting for age and accounting for subject-level correlations in the subset analyses revealed no association between PTA (9 - 12 kHz) and outcomes of interest.

CONCLUSIONS

EHF thresholds show age-, sex-, and race-related patterns of elevation that are similar to what is observed for conventional thresholds. The current results support the need for more research to determine the utility of adding EHF thresholds to routine audiometric assessment with middle-aged and older adults.

Increased listening effort and cochlear neural degeneration underlie behavioral deficits in speech perception in noise in normal hearing middle-aged adults

Middle-age is a critical period of rapid changes in brain function that presents an opportunity for early diagnostics and intervention for neurodegenerative conditions later in life. Hearing loss is one such early indicator linked to many comorbidities later in life. However, current clinical tests fail to capture hearing difficulties for ∼10% of middle-aged adults seeking help at hearing clinics. Cochlear neural degeneration (CND) could play a role in these hearing deficits, but our current understanding is limited by the lack of objective diagnostics and uncertainty regarding its perceptual consequences. Here, using a cross-species approach, we measured envelope following responses (EFRs) - neural ensemble responses to sound originating from the peripheral auditory pathway - in young and middle-aged adults with normal audiometric thresholds, and compared these responses to young and middle-aged Mongolian gerbils, where CND was histologically confirmed. We observed near identical changes in EFRs across species that were associated with CND. Perceptual effects measured as behavioral readouts showed deficits in the most challenging listening conditions and were associated with CND. Additionally, pupil-indexed listening effort increased even at moderate task difficulties where behavioral outcomes were matched. Our results reveal perceptual deficits in middle-aged adults driven by CND and increases in listening effort, which may result in increased listening fatigue and conversational disengagement.

A longitudinal study investigating the effects of noise exposure on behavioural, electrophysiological and self-report measures of hearing in musicians with normal audiometric thresholds

Musicians are at risk of hearing loss and tinnitus due to regular exposure to high levels of noise. This level of risk may have been underestimated previously since damage to the auditory system, such as cochlear synaptopathy, may not be easily detectable using standard clinical measures. Most previous research investigating hearing loss in musicians has involved cross-sectional study designs that may capture only a snapshot of hearing health in relation to noise exposure. The aim of this study was to investigate the effects of cumulative noise exposure on behavioural, electrophysiological, and self-report indices of hearing damage in early-career musicians and non-musicians with normal hearing over a 2-year period. Participants completed an annual test battery consisting of pure tone audiometry, extended high-frequency hearing thresholds, distortion product otoacoustic emissions (DPOAEs), speech perception in noise, auditory brainstem responses, and self-report measures of tinnitus, hyperacusis, and hearing in background noise. Participants also completed the Noise Exposure Structured Interview to estimate cumulative noise exposure across the study period. Linear mixed models assessed changes over time. The longitudinal analysis comprised 64 early-career musicians (female n = 34; age range at T0 = 18-26 years) and 30 non-musicians (female n = 20; age range at T0 = 18-27 years). There were few longitudinal changes as a result of musicianship. Small improvements over time in some measures may be attributable to a practice/test-retest effect. Some measures (e.g., DPOAE indices of outer hair cell function) were associated with noise exposure at each time point, but did not show a significant change over time. A small proportion of participants reported a worsening of their tinnitus symptoms, which participants attributed to noise exposure, or not using hearing protection. Future longitudinal studies should attempt to capture the effects of noise exposure over a longer period, taken at several time points, for a precise measure of how hearing changes over time. Hearing conservation programmes for "at risk" individuals should closely monitor DPOAEs to detect early signs of noise-induced hearing loss when audiometric thresholds are clinically normal.

Description of a new low-cost and open-source audiometer and its validation with normal-hearing listeners: The Aupiometer

Hearing loss is a major public health problem. In 2050, it could affect 2.5 billion people. It has therefore become necessary to prevent and diagnose them as early and as widely as possible. However, the costs of clinical equipment dedicated to the functional exploration of hearing remain high and hamper their distribution, while the technologies used are relatively basic. For example, the gold-standard pure-tone audiometry (PTA) essentially consists of emitting pure sounds. In addition, clinical audiometers are generally limited to PTA or few audiological tests, while hearing loss induce multiple functional deficits. Here, we present the Aupiometer, a low-cost audiometer implemented on a modular open-source system based on Raspberry Pi, and which integrates the entire technical framework necessary to carry out audiological measurements. Several hearing tests are already implemented (e.g. PTA, speech audiometry, questionnaires), while the clinical validity of the Aupiometer was verified on a panel of participants (N = 16) for an automated test of standard and extended high-frequency PTA, from 0.125 to 16 kHz, in comparison with a clinical audiometer. For this comparison between the two devices and over this wide frequency range, the difference is evaluated as less than ±10 dB for a 90% confidence interval, of the same order of magnitude as on test-retest differences on a single device. The interest of this device also extends to academic research as it should encourage the prototyping of innovative hearing tests by the community, in order to better understand the diversity of hearing problems in the population.

Band importance for speech-in-speech recognition in the presence of extended high-frequency cues

Band importance functions for speech-in-noise recognition, typically determined in the presence of steady background noise, indicate a negligible role for extended high frequencies (EHFs; 8-20 kHz). However, recent findings indicate that EHF cues support speech recognition in multi-talker environments, particularly when the masker has reduced EHF levels relative to the target. This scenario can occur in natural auditory scenes when the target talker is facing the listener, but the maskers are not. In this study, we measured the importance of five bands from 40 to 20 000 Hz for speech-in-speech recognition by notch-filtering the bands individually. Stimuli consisted of a female target talker recorded from 0° and a spatially co-located two-talker female masker recorded either from 0° or 56.25°, simulating a masker either facing the listener or facing away, respectively. Results indicated peak band importance in the 0.4-1.3 kHz band and a negligible effect of removing the EHF band in the facing-masker condition. However, in the non-facing condition, the peak was broader and EHF importance was higher and comparable to that of the 3.3-8.3 kHz band in the facing-masker condition. These findings suggest that EHFs contain important cues for speech recognition in listening conditions with mismatched talker head orientations.

The relationship between distortion product otoacoustic emissions and audiometric thresholds in the extended high-frequency range

Distortion product otoacoustic emissions (DPOAEs) and behavioral audiometry are routinely used for hearing screening and assessment. These measures provide related information about hearing status as both are sensitive to cochlear pathologies. However, DPOAE testing is quicker and does not require a behavioral response. Despite these practical advantages, DPOAE testing is often limited to screening only low and mid- frequencies. Variation in ear canal acoustics across ears and probe placements has resulted in less reliable measurements of DPOAEs near 4 kHz and above where standing waves commonly occur. Stimulus calibration in forward pressure level and responses in emitted pressure level can reduce measurement variability. Using these calibrations, this study assessed the correlation between audiometry and DPOAEs in the extended high frequencies where stimulus calibrations and responses are most susceptible to the effect of standing waves. Behavioral thresholds and DPOAE amplitudes were negatively correlated, and DPOAE amplitudes in emitted pressure level accounted for twice as much variance as amplitudes in sound pressure level. Both measures were correlated with age. These data show that with appropriate calibration methods, extended high-frequency DPOAEs are sensitive to differences in audiometric thresholds and highlight the need to consider calibration techniques in clinical and research applications of DPOAEs.

Effect of age-related extended high frequency hearing loss on the subjective impressions of dental drill noise

Fear and anxiety among patients are sometimes evoked in dental clinics due to the sound of dental drills. This study aimed to explore the impact of age-related hearing loss in the extended high frequency (EHF) range above 8 kHz on individuals' subjective discomfort towards dental drill noise. After measuring pure-tone audiometric thresholds at both conventional and extended high frequencies, we used a psychoacoustic approach to evaluate subjective impressions of four dental drill sound stimuli, which featured varying frequency components, in 62 participants (aged 12-67 years). We found a significant decrease in hearing sensitivity within the EHF range as age increased, with notable differences in hearing thresholds at 14 kHz between teenage and older adults exceeding 65 dB. Furthermore, significant differences were observed between younger and older (above 40 years) participants in the subjective impressions of dental drill noise, emphasizing age as a critical factor in the perception of high frequency components. Consequently, age may influence the unpleasantness of dental drilling noise. Compared to older individuals, young participants may exhibit increased fear of dental procedures owing to physiological factors. These results underscore the need for age-appropriate noise control strategies in dental clinics to mitigate anxiety and improve patient comfort.

Exposure to Noise or Music in Clinical Trials: A Scoping Review on Ethical and Methodological Considerations

BACKGROUND

Use of noise or music in experimental human studies requires balancing the need to avoid subjecting participants to potentially harmful noise levels while still reaching levels that will produce a measurable change in the primary outcome. Several methodological and ethical aspects must be considered. This study aims to summarize ethical and methodological aspects, and reported outcomes, of previously published experimental paradigms using loud noise/music.

METHODS AND MATERIALS

Four databases (Medline, Central, Web of Science, and Scopus) and two trials registries (Clinicaltrials.gov and EU Clinical Trials) were searched. Extracted items had the details of author and year of publication, study design and purpose, population, setting timeline and material, selected battery test, and effect of noise/music on participants' hearing.

RESULTS

Thirty-four studies were included. Exposure safety considerations were reported in five studies. Eleven studies assessing hearing loss used white or narrow-band noise [(NBN (0.5-4 kHz), up to 115 dBA, duration range: 3'-24 hours)], and 10 used pop music (up to 106 dBA, duration range: 10'-4 hours). Experimental setting varied significantly. Temporary thresholds shift (TTS) and reduction in distortion product otoacoustic emissions were found at 1-8 kHz, with maximum average TTS∼21.5 dB at 4 kHz after NBN and ∼11.5 dB at 6 kHz after music exposure. All participants recovered their hearing, except for one participant in one study. In the 13 non-hearing loss studies, no hearing testing was performed after exposure, but loud noise was associated with temporary stress, bradygastria, and cardiovascular changes. Noise-induced subjective stress may be higher for participants with tinnitus. Loud noise (100 dBA, 10') increased diastolic and mean blood pressure only in participants with hypertension.

CONCLUSION

Experimental exposure paradigms can produce temporary changes to hearing without measurable long-term health consequences. Methodological and ethical aspects identified in this review should be considered for the development of future paradigms.

Predictors of Speech-in-Noise Understanding in a Population of Occupationally Noise-Exposed Individuals

Understanding speech in noise is particularly difficult for individuals occupationally exposed to noise due to a mix of noise-induced auditory lesions and the energetic masking of speech signals. For years, the monitoring of conventional audiometric thresholds has been the usual method to check and preserve auditory function. Recently, suprathreshold deficits, notably, difficulties in understanding speech in noise, has pointed out the need for new monitoring tools. The present study aims to identify the most important variables that predict speech in noise understanding in order to suggest a new method of hearing status monitoring. Physiological (distortion products of otoacoustic emissions, electrocochleography) and behavioral (amplitude and frequency modulation detection thresholds, conventional and extended high-frequency audiometric thresholds) variables were collected in a population of individuals presenting a relatively homogeneous occupational noise exposure. Those variables were used as predictors in a statistical model (random forest) to predict the scores of three different speech-in-noise tests and a self-report of speech-in-noise ability. The extended high-frequency threshold appears to be the best predictor and therefore an interesting candidate for a new way of monitoring noise-exposed professionals.

Cochlear-Implant Simulated Signal Degradation Exacerbates Listening Effort in Older Listeners

OBJECTIVES

Individuals with cochlear implants (CIs) often report that listening requires high levels of effort. Listening effort can increase with decreasing spectral resolution, which occurs when listening with a CI, and can also increase with age. What is not clear is whether these factors interact; older CI listeners potentially experience even higher listening effort with greater signal degradation than younger CI listeners. This study used pupillometry as a physiological index of listening effort to examine whether age, spectral resolution, and their interaction affect listening effort in a simulation of CI listening.

DESIGN

Fifteen younger normal-hearing listeners (ages 18 to 31 years) and 15 older normal-hearing listeners (ages 65 to 75 years) participated in this experiment; they had normal hearing thresholds from 0.25 to 4 kHz. Participants repeated sentences presented in quiet that were either unprocessed or vocoded, simulating CI listening. Stimuli frequency spectra were limited to below 4 kHz (to control for effects of age-related high-frequency hearing loss), and spectral resolution was decreased by decreasing the number of vocoder channels, with 32-, 16-, and 8-channel conditions. Behavioral speech recognition scores and pupil dilation were recorded during this task. In addition, cognitive measures of working memory and processing speed were obtained to examine if individual differences in these measures predicted changes in pupil dilation.

RESULTS

For trials where the sentence was recalled correctly, there was a significant interaction between age and spectral resolution, with significantly greater pupil dilation in the older normal-hearing listeners for the 8- and 32-channel vocoded conditions. Cognitive measures did not predict pupil dilation.

CONCLUSIONS

There was a significant interaction between age and spectral resolution, such that older listeners appear to exert relatively higher listening effort than younger listeners when the signal is highly degraded, with the largest effects observed in the eight-channel condition. The clinical implication is that older listeners may be at higher risk for increased listening effort with a CI.

Effects of Stimulus Type on 16-kHz Detection Thresholds

OBJECTIVES

Audiometric testing typically does not include frequencies above 8 kHz. However, recent research suggests that extended high-frequency (EHF) sensitivity could affect hearing in natural communication environments. Clinical assessment of hearing often employs pure tones and frequency-modulated (FM) tones interchangeably regardless of frequency. The present study was designed to evaluate how the stimulus chosen to measure EHF thresholds affects estimates of hearing sensitivity.

DESIGN

The first experiment used standard audiometric procedures to measure 8- and 16-kHz thresholds for 5- to 28-year olds with normal hearing in the standard audiometric range (250 to 8000 Hz). Stimuli were steady tones, pulsed tones, and FM tones. The second experiment tested 18- to 28-year olds with normal hearing in the standard audiometric range using psychophysical procedures to evaluate how changes in sensitivity as a function of frequency affect detection of stimuli that differ with respect to bandwidth, including bands of noise. Thresholds were measured using steady tones, pulsed tones, FM tones, narrow bands of noise, and one-third-octave bands of noise at a range of center frequencies in one ear.

RESULTS

In experiment 1, thresholds improved with increasing age at 8 kHz and worsened with increasing age at 16 kHz. Thresholds for individual participants were relatively similar for steady, pulsed, and FM tones at 8 kHz. At 16 kHz, mean thresholds were approximately 5 dB lower for FM tones than for steady or pulsed tones. This stimulus effect did not differ as a function of age. Experiment 2 replicated this greater stimulus effect at 16 kHz than at 8 kHz and showed that the slope of the audibility curve accounted for these effects.

CONCLUSIONS

Contrary to prior expectations, there was no evidence that the choice of stimulus type affected school-age children more than adults. For individual participants, audiometric thresholds at 16 kHz were as much as 20 dB lower for FM tones than for steady tones. Threshold differences across stimuli at 16 kHz were predicted by differences in audibility across frequency, which can vary markedly between listeners. These results highlight the importance of considering spectral width of the stimulus used to evaluate EHF thresholds.

Subcortical Auditory Processing and Speech Perception in Noise Among Individuals With and Without Extended High-Frequency Hearing Loss

PURPOSE

The significance of extended high-frequency (EHF) hearing (> 8 kHz) is not well understood so far. In this study, we aimed to understand the relationship between EHF hearing loss (EHFHL) and speech perception in noise (SPIN) and the associated physiological signatures using the speech-evoked frequency-following response (sFFR).

METHOD

Sixteen young adults with EHFHL and 16 age- and sex-matched individuals with normal hearing participated in the study. SPIN performance in right speech-right noise, left speech-left noise, and binaural listening conditions was evaluated using the Turkish Matrix Test. Additionally, subcortical auditory processing was assessed by recording sFFRs elicited by 40-ms /da/ stimuli.

RESULTS

Individuals with EHFHL demonstrated poorer SPIN performances in all listening conditions (p < .01). Longer latencies were observed in the V (onset) and O (offset) peaks in these individuals (p ≤ .01). However, only the V/A peak amplitude was found to be significantly reduced in individuals with EHFHL (p < .01).

CONCLUSIONS

Our findings highlight the importance of EHF hearing and suggest that EHF hearing should be considered among the key elements in SPIN. Individuals with EHFHL show a tendency toward weaker subcortical auditory processing, which likely contributes to their poorer SPIN performance. Thus, routine assessment of EHF hearing should be implemented in clinical settings, alongside the evaluation of standard audiometric frequencies (0.25-8 kHz).

Polygenic Risk Score-Based Association Analysis of Speech-in-Noise and Hearing Threshold Measures in Healthy Young Adults with Self-reported Normal Hearing

PURPOSE

Speech-in-noise (SIN) traits exhibit high inter-subject variability, even for healthy young adults reporting normal hearing. Emerging evidence suggests that genetic variability could influence inter-subject variability in SIN traits. Genome-wide association studies (GWAS) have uncovered the polygenic architecture of various adult-onset complex human conditions. Polygenic risk scores (PRS) summarize complex genetic susceptibility to quantify the degree of genetic risk for health conditions. The present study conducted PRS-based association analyses to identify PRS risk factors for SIN and hearing threshold measures in 255 healthy young adults (18-40 years) with self-reported normal hearing.

METHODS

Self-reported SIN perception abilities were assessed by the Speech, Spatial, and Qualities of Hearing Scale (SSQ12). QuickSIN and audiometry (0.25-16 kHz) were performed on 218 participants. Saliva-derived DNA was used for low-pass whole genome sequencing, and 2620 PRS variables for various traits were calculated using the models derived from the polygenic risk score (PGS) catalog. The regression analysis was conducted to identify predictors for SSQ12, QuickSIN, and better ear puretone averages at conventional (PTA0.5-2), high (PTA4-8), and extended-high (PTA12.5-16) frequency ranges.

RESULTS

Participants with a higher genetic predisposition to HDL cholesterol reported better SSQ12. Participants with high PRS to dementia revealed significantly elevated PTA4-8, and those with high PRS to atrial fibrillation and flutter revealed significantly elevated PTA12.5-16.

CONCLUSION

These results indicate that healthy individuals with polygenic risk of certain health conditions could exhibit a subclinical decline in hearing health measures at young ages, decades before clinically meaningful SIN deficits and hearing loss could be observed. PRS could be used to identify high-risk individuals to prevent hearing health conditions by promoting a healthy lifestyle.

Differential benefits of unmasking extended high-frequency content of target or background speech

Current evidence supports the contribution of extended high frequencies (EHFs; >8 kHz) to speech recognition, especially for speech-in-speech scenarios. However, it is unclear whether the benefit of EHFs is due to phonetic information in the EHF band, EHF cues to access phonetic information at lower frequencies, talker segregation cues, or some other mechanism. This study investigated the mechanisms of benefit derived from a mismatch in EHF content between target and masker talkers for speech-in-speech recognition. EHF mismatches were generated using full band (FB) speech and speech low-pass filtered at 8 kHz. Four filtering combinations with independently filtered target and masker speech were used to create two EHF-matched and two EHF-mismatched conditions for one- and two-talker maskers. Performance was best with the FB target and the low-pass masker in both one- and two-talker masker conditions, but the effect was larger for the two-talker masker. No benefit of an EHF mismatch was observed for the low-pass filtered target. A word-by-word analysis indicated higher recognition odds with increasing EHF energy level in the target word. These findings suggest that the audibility of target EHFs provides target phonetic information or target segregation and selective attention cues, but that the audibility of masker EHFs does not confer any segregation benefit.

Speech understanding and extended high-frequency hearing sensitivity in blast-exposed veteransa)

Auditory difficulties reported by normal-hearing Veterans with a history of blast exposure are primarily thought to stem from processing deficits in the central nervous system. However, previous work on speech understanding in noise difficulties in this patient population have only considered peripheral hearing thresholds in the standard audiometric range. Recent research suggests that variability in extended high-frequency (EHF; >8 kHz) hearing sensitivity may contribute to speech understanding deficits in normal-hearing individuals. Therefore, this work was designed to identify the effects of blast exposure on several common clinical speech understanding measures and EHF hearing sensitivity. This work also aimed to determine whether variability in EHF hearing sensitivity contributes to speech understanding difficulties in normal-hearing blast-exposed Veterans. Data from 41 normal- or near-normal-hearing Veterans with a history of blast exposure and 31 normal- or near-normal-hearing control participants with no history of head injury were employed in this study. Analysis identified an effect of blast exposure on several speech understanding measures but showed no statistically significant differences in EHF thresholds between participant groups. Data showed that variability in EHF hearing sensitivity did not contribute to group-related differences in speech understanding, although study limitations impact interpretation of these results.

Preclinical prospects of investigational agents for hearing loss treatment

INTRODUCTION

: Hearing loss has a high prevalence, with aging, noise exposure, ototoxic drug therapies, and genetic mutations being some of the leading causes of hearing loss. Health conditions such as cardiovascular disease and diabetes are associated with hearing loss, perhaps due to shared vascular pathology in the ear and in other tissues.

AREAS COVERED

: Issues in the design of preclinical research preclude the ability to make comparisons regarding the relative efficacy of different drugs of interest for possible hearing loss prevention or hearing restoration. This has not slowed the advancement of candidate therapeutics into human clinical testing. There is a robust pipeline with drugs that have different mechanisms of action providing diverse candidate therapies and opportunities for combination therapies to be considered.

EXPERT OPINION

: Much of the preclinical research literature lacks standard study design elements such as dose response testing, and lack of standardization of test protocols significantly limits conclusions regarding relative efficacy. Nonetheless, the many positive results to date have supported translation of preclinical efforts into clinical trials assessing potential human benefits. Approval of the first hearing loss prevention therapeutic is a major success, providing a pathway for other drugs to follow.

Defining Hearing Loss Severity Based on Pure-Tone Audiometry and Self-Reported Perceived Hearing Difficulty: National Health and Nutrition Examination Survey

BACKGROUND

 There is a well-known metric to describe average/normal vision, 20/20, but the same agreed-upon standard does not exist for hearing. The pure-tone average has been advocated for such a metric.

PURPOSE

 We aimed to use a data-driven approach to inform a universal metric for hearing status based on pure-tone audiometry and perceived hearing difficulty (PHD).

RESEARCH DESIGN

 This is a cross-sectional national representative survey of the civilian noninstitutionalized population in the United States.

STUDY SAMPLE

 Data from the 2011-2012 and 2015-2016 cycles of the National Health and Nutrition Examination Survey (NHANES) were used in our analysis. Of 9,444 participants aged 20 to 69 years from the 2011-2012 and 2015-2016 cycles, we excluded those with missing self-reported hearing difficulty (n = 8) and pure-tone audiometry data (n = 1,361). The main analysis sample, therefore, included 8,075 participants. We completed a subanalysis limited to participants with "normal" hearing based on the World Health Organization (WHO) standard (pure-tone average, PTA of 500, 1000, 2000, 4000 Hz < 20 dBHL).

ANALYSIS

 Descriptive analyses to calculate means and proportions were used to describe characteristics of the analysis sample across PHD levels relative to PTA. Four PTAs were compared, low frequency (LF-PTA, 500, 1,000, 2,000 Hz), four-frequency PTA (PTA4, 500, 1,000, 2,000, 4,000 Hz), high frequency (HF-PTA, 4,000, 6,000, 8,000 Hz), and all frequency (AF-PTA, 500, 1,000, 2,000, 4,000, 6,000, 8,000 Hz). Differences between groups were tested using Rao-Scott χ2 tests for categorical variables and F tests for continuous variables. Logistic regression was used to plot receiver operating characteristic curves with PHD as a function of PTA. The sensitivity and specificity for each PTA and PHD were also calculated.

RESULTS

 We found that 19.61% of adults aged 20 to 69 years reported PHD, with only 1.41% reporting greater than moderate PHD. The prevalence of reported PHD increased with higher decibel hearing levels (dBHL) categories reaching statistical significance (p < 0.05 with Bonferroni correction) at 6 to 10 dBHL for PTAs limited to lower frequencies (LF-PTA and PTA4) and 16 to 20 dBHL when limited to higher frequencies (HF-PTA). The prevalence of greater than moderate PHD reached statistical significance at 21 to 30 dBHL when limited to lower frequencies (LF-PTA) and 41 to 55 dBHL when limited to higher frequencies (HF-PTA). Forty percent of the sample had high-frequency loss with "normal" low-frequency hearing, representing nearly 70% of hearing loss configurations. The diagnostic accuracy of the PTAs for reported PHD was poor to sufficient (<0.70); however, the HF-PTA had the highest sensitivity (0.81).

CONCLUSION

 We provide four basic recommendations based on our analysis: (1) a PTA-based metric for hearing ability should include frequencies above 4,000 Hz; (2) the data-driven dBHL cutoff for any PHD/"normal" hearing is 15 dBHL; (3) when considering greater than moderate PHD, the data-driven cutoffs were more variable but estimated at 20 to 30 dBHL for LF-PTA, 30 to 35 dBHL for PTA4, 25 to 50 dBHL for AF-PTA, and 40 to 65 dBHL for HF-PTA; and (4) clinical recommendations and legislative agendas should include consideration beyond pure-tone audiometry such as functional assessment of hearing and PHD.

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.

Evaluation of hidden hearing loss in normal-hearing firearm users

Some noise exposures resulting in temporary threshold shift (TTS) result in cochlear synaptopathy. The purpose of this retrospective study was to evaluate a human population that might be at risk for noise-induced cochlear synaptopathy (i.e., "hidden hearing loss"). Participants were firearm users who were (1) at-risk for prior audiometric noise-induced threshold shifts, given their history of firearm use, (2) likely to have experienced complete threshold recovery if any prior TTS had occurred, based on this study's normal-hearing inclusion criteria, and (3) not at-risk for significant age-related synaptopathic loss, based on this study's young-adult inclusion criteria. 70 participants (age 18-25 yr) were enrolled, including 33 firearm users experimental (EXP), and 37 non-firearm users control (CNTRL). All participants were required to exhibit audiometric thresholds ≤20 dB HL bilaterally, from 0.25 to 8 kHz. The study was designed to test the hypothesis that EXP participants would exhibit a reduced cochlear nerve response compared to CNTRL participants, despite normal-hearing sensitivity in both groups. No statistically significant group differences in auditory performance were detected between the CNTRL and EXP participants on standard audiom to etry, extended high-frequency audiometry, Words-in-Noise performance, distortion product otoacoustic emission, middle ear muscle reflex, or auditory brainstem response. Importantly, 91% of EXP participants reported that they wore hearing protection either "all the time" or "almost all the time" while using firearms. The data suggest that consistent use of hearing protection during firearm use can effectively protect cochlear and neural measures of auditory function, including suprathreshold responses. The current results do not exclude the possibility that neural pathology may be evident in firearm users with less consistent hearing protection use. However, firearm users with less consistent hearing protection use are also more likely to exhibit threshold elevation, among other cochlear deficits, thereby confounding the isolation of any potentially selective neural deficits. Taken together, it seems most likely that firearm users who consistently and correctly use hearing protection will exhibit preserved measures of cochlear and neural function, while firearm users who inconsistently and incorrectly use hearing protection are most likely to exhibit cochlear injury, rather than evidence of selective neural injury in the absence of cochlear injury.

On the use of the TIMIT, QuickSIN, NU-6, and other widely used bandlimited speech materials for speech perception experiments

The use of spectrally degraded speech signals deprives listeners of acoustic information that is useful for speech perception. Several popular speech corpora, recorded decades ago, have spectral degradations, including limited extended high-frequency (EHF) (>8 kHz) content. Although frequency content above 8 kHz is often assumed to play little or no role in speech perception, recent research suggests that EHF content in speech can have a significant beneficial impact on speech perception under a wide range of natural listening conditions. This paper provides an analysis of the spectral content of popular speech corpora used for speech perception research to highlight the potential shortcomings of using bandlimited speech materials. Two corpora analyzed here, the TIMIT and NU-6, have substantial low-frequency spectral degradation (<500 Hz) in addition to EHF degradation. We provide an overview of the phenomena potentially missed by using bandlimited speech signals, and the factors to consider when selecting stimuli that are sensitive to these effects.

The audiogram: Detection of pure-tone stimuli in ototoxicity monitoring and assessments of investigational medicines for the inner ear

Pure-tone thresholds have long served as a gold standard for evaluating hearing sensitivity and documenting hearing changes related to medical treatments, toxic or otherwise hazardous exposures, ear disease, genetic disorders involving the ear, and deficits that develop during aging. Although the use of pure-tone audiometry is basic and standard, interpretation of thresholds obtained at multiple frequencies in both ears over multiple visits can be complex. Significant additional complexity is introduced when audiometric tests are performed within ototoxicity monitoring programs to determine if hearing loss occurs as an adverse reaction to an investigational medication and during the design and conduct of clinical trials for new otoprotective agents for noise and drug-induced hearing loss. Clinical trials using gene therapy or stem cell therapy approaches are emerging as well with audiometric outcome selection further complicated by safety issues associated with biological therapies. This review addresses factors that must be considered, including test-retest variability, significant threshold change definitions, use of ototoxicity grading scales, interpretation of early warning signals, measurement of notching in noise-induced hearing loss, and application of age-based normative data to interpretation of pure-tone thresholds. Specific guidance for clinical trial protocols that will assure rigorous methodological approaches and interpretable audiometric data are provided.