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

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.

Effects of Noise Exposure on Peripheral Auditory Function, Binaural Envelope Coding, and Speech Perception in Student Musicians With Normal Hearing

OBJECTIVES

Musicians face an increased risk of hearing loss due to prolonged and repetitive exposure to high-noise levels. Detecting early signs of hearing loss, which are subtle and often elusive to traditional clinical tests like pure-tone audiometry, is essential. The objective of this study was to investigate the impact of noise exposure on the electrophysiological and perceptual aspects of subclinical hearing damage in young musicians with normal audiometric thresholds.

DESIGN

The study included 33 musicians and 33 nonmusicians, all aged between 21 and 35 years, with normal audiometric thresholds. Participants underwent a comprehensive test battery, which encompassed standard and extended high-frequency (EHF) pure-tone audiometry (0.25 to 16 kHz), a Noise Exposure Structured Interview, auditory brainstem responses (ABRs) to clicks at various presentation rates and levels, thresholds for detecting interaural envelope time difference, and a spatial release from masking (SRM) paradigm in which the target speech was presented in the presence of either colocated or spatially separated time-reversed two-talker babble.

RESULTS

The results indicated the musician group reported greater lifetime noise exposure than the nonmusician group, but the Noise Exposure Structured Interview scores were neither correlated with the ABR results nor with the speech perception outcomes. The ABR analyses indicated diminished level-dependent growth and increased rate-dependent decline in wave I amplitudes among musicians compared with nonmusicians. The student musicians exhibited better binaural envelope processing skills than nonmusicians, emphasizing their perceptual advantages in auditory processing associated with musicianship. Speech perception results indicated no significant differences in SRM between student musicians and nonmusicians. However, in both groups, individuals with poorer EHF hearing exhibited reduced SRM compared with those with normal EHF hearing, underscoring the importance of assessing and addressing EHF hearing.

CONCLUSIONS

Student musicians exhibit peripheral neural deficits; however, no clear relation was found between these neural deficits and their perceptual skills. Notably, reduced EHF thresholds were clearly related to reduced SRM, which poses a challenge for speech perception in complex multi-talker environments, affecting both musicians and nonmusicians alike.

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.

Gender and speech material effects on the long-term average speech spectrum, including at extended high frequencies

Gender and language effects on the long-term average speech spectrum (LTASS) have been reported, but typically using recordings that were bandlimited and/or failed to accurately capture extended high frequencies (EHFs). Accurate characterization of the full-band LTASS is warranted given recent data on the contribution of EHFs to speech perception. The present study characterized the LTASS for high-fidelity, anechoic recordings of males and females producing Bamford-Kowal-Bench sentences, digits, and unscripted narratives. Gender had an effect on spectral levels at both ends of the spectrum: males had higher levels than females below approximately 160 Hz, owing to lower fundamental frequencies; females had ∼4 dB higher levels at EHFs, but this effect was dependent on speech material. Gender differences were also observed at ∼300 Hz, and between 800 and 1000 Hz, as previously reported. Despite differences in phonetic content, there were only small, gender-dependent differences in EHF levels across speech materials. EHF levels were highly correlated across materials, indicating relative consistency within talkers. Our findings suggest that LTASS levels at EHFs are influenced primarily by talker and gender, highlighting the need for future research to assess whether EHF cues are more audible for female speech than for male speech.

Midlife Speech Perception Deficits: Impact of Extended High-Frequency Hearing, Peripheral Neural Function, and Cognitive Abilities

OBJECTIVES

The objectives of the present study were to investigate the effects of age-related changes in extended high-frequency (EHF) hearing, peripheral neural function, working memory, and executive function on speech perception deficits in middle-aged individuals with clinically normal hearing.

DESIGN

We administered a comprehensive assessment battery to 37 participants spanning the age range of 20 to 56 years. This battery encompassed various evaluations, including standard and EHF pure-tone audiometry, ranging from 0.25 to 16 kHz. In addition, we conducted auditory brainstem response assessments with varying stimulation rates and levels, a spatial release from masking (SRM) task, and cognitive evaluations that involved the Trail Making test (TMT) for assessing executive function and the Abbreviated Reading Span test (ARST) for measuring working memory.

RESULTS

The results indicated a decline in hearing sensitivities at EHFs and an increase in completion times for the TMT with age. In addition, as age increased, there was a corresponding decrease in the amount of SRM. The declines in SRM were associated with age-related declines in hearing sensitivity at EHFs and TMT performance. While we observed an age-related decline in wave I responses, this decline was primarily driven by age-related reductions in EHF thresholds. In addition, the results obtained using the ARST did not show an age-related decline. Neither the auditory brainstem response results nor ARST scores were correlated with the amount of SRM.

CONCLUSIONS

These findings suggest that speech perception deficits in middle age are primarily linked to declines in EHF hearing and executive function, rather than cochlear synaptopathy or working memory.

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.

Digits-in-Noise Test as an Assessment Tool for Hearing Loss and Hearing Aids

The aim of this study was to examine the relationship between an American English Digits in Noise (DIN) test and commonly used audiological measures to evaluate the DIN test's ability to detect hearing loss and validate hearing aid fitting. QuickSIN and DIN tests were completed by participants with untreated hearing loss (n = 46), prescription hearing aids (n = 15), and over-the-counter (OTC) hearing aids (n = 12). Performance on the QuickSIN showed moderate positive correlations with DIN for untreated hearing loss participants and prescription hearing aid users, but not for OTC hearing aid users. For untreated hearing loss participants, both QuickSIN and DIN tests showed positive moderate to strong correlations with high frequency puretone averages. In OTC users, DIN scores did not significantly change over a 6-month time period and were better when conducted remotely compared to in-person testing. Our results suggest that the DIN test may be a feasible monitoring option for individuals with hearing loss and those fitted with hearing aids. However, due to small sample size in this pilot study, future research is needed to examine DIN test's utility for fitting and validating OTC hearing aids.

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.

Reconsidering classic ideas in speech communication

The papers in this special issue provide a critical look at some historical ideas that have had an influence on research and teaching in the field of speech communication. They also address widely used methodologies or address long-standing methodological challenges in the areas of speech perception and speech production. The goal is to reconsider and evaluate the need for caution or replacement of historical ideas with more modern results and methods. The contributions provide respectful historical context to the classic ideas, as well as new original research or discussion that clarifies the limitations of the original ideas.