Reliability and Repeatability of the Speech Cue Profile

Contributions of Behavioral and Electrophysiological Spectrotemporal Processing to the Perception of Degraded Speech in Younger and Older Adults

PURPOSE

The aim of this study was to evaluate (a) the effect of aging on spectral and temporal resolution, as measured both behaviorally and electrophysiologically, and (b) the contributions of spectral and temporal resolution and cognition to speech perception in younger and older adults.

METHOD

Eighteen younger and 18 older listeners with normal hearing or no more than mild-moderate hearing loss participated in this cross-sectional study. Speech recognition was assessed with the QuickSIN test and six-band noise-vocoded sentences. Frequency discrimination, temporal interval discrimination, and gap detection thresholds were obtained using a three-alternative forced-choice task. Cortical auditory evoked potentials were recorded in response to tonal frequency changes and to gaps in noise. Cognitive testing included nonverbal reasoning, vocabulary, working memory, and processing speed.

RESULTS

There were age-related declines on many outcome measures, including speech perception in noise, cognition (nonverbal reasoning, processing speed), behavioral gap detection thresholds, and neural correlates of spectral and temporal processing (smaller P1 amplitudes and prolonged P2 latencies in response to frequency change; smaller N1-P2 amplitudes and longer P1, N1, P2 latencies to temporal gaps). Hearing thresholds and neural processing of spectral and temporal information were the main predictors of degraded speech recognition performance, in addition to cognition and perceptual learning. These factors accounted for 58% of the variability on the QuickSIN test and 41% of variability on the noise-vocoded speech.

CONCLUSIONS

The results confirm and extend previous work demonstrating age-related declines in gap detection, cognition, and neural processing of spectral and temporal features of sounds. Neural measures of spectral and temporal processing were better predictors of speech perception than behavioral ones.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.28883711.

Age and masking effects on acoustic cues for vowel categorizationa)

Age-related changes in auditory processing may reduce physiological coding of acoustic cues, contributing to older adults' difficulty perceiving speech in background noise. This study investigated whether older adults differed from young adults in patterns of acoustic cue weighting for categorizing vowels in quiet and in noise. All participants relied primarily on spectral quality to categorize /ɛ/ and /æ/ sounds under both listening conditions. However, relative to young adults, older adults exhibited greater reliance on duration and less reliance on spectral quality. These results suggest that aging alters patterns of perceptual cue weights that may influence speech recognition abilities.

Ecological Validity, External Validity, and Mundane Realism in Hearing Science

Tests of hearing function are typically conducted in conditions very different from those in which people need to hear and communicate. Even when test conditions are more similar, they cannot represent the diversity of situations that may be encountered by individuals in daily life. As a consequence, it is necessary to consider external validity: the extent to which findings are likely to generalize to conditions beyond those in which data are collected. External validity has long been a concern in many fields and has led to the development of theories and methods aimed at improving generalizability of laboratory findings. Within hearing science, along with related fields, efforts to address generalizability have come to focus heavily on realism: the extent to which laboratory conditions are similar to conditions found in everyday settings of interest. In fact, it seems that realism is now tacitly equated with generalizability. The term that has recently been applied to this approach by many researchers is ecological validity . Recent usage of the term ecological validity within hearing science, as well as other fields, is problematic for three related reasons: (i) it encourages the conflation of the separate concepts of realism and validity; (ii) it diverts attention from the need for methods of quantifying generalization directly; and (iii) it masks a useful longstanding definition of ecological validity within the field of ecological psychology. The definition of ecological validity first used within ecological psychology-the correlation between cues received at the peripheral nervous system and the identity of distant objects or events in the environment-is entirely different from its current usage in hearing science and many related fields. However, as part of an experimental approach known as representative design , the original concept of ecological validity can play a valuable role in facilitating generalizability. This paper will argue that separate existing terms should be used when referring to realism and generalizability, and that the definition of ecological validity provided by the Lens Model may be a valuable conceptual tool within hearing science.

Relating Suprathreshold Auditory Processing Abilities to Speech Understanding in Competition

(1) Background: Difficulty hearing in noise is exacerbated in older adults. Older adults are more likely to have audiometric hearing loss, although some individuals with normal pure-tone audiograms also have difficulty perceiving speech in noise. Additional variables also likely account for speech understanding in noise. It has been suggested that one important class of variables is the ability to process auditory information once it has been detected. Here, we tested a set of these “suprathreshold” auditory processing abilities and related them to performance on a two-part test of speech understanding in competition with and without spatial separation of the target and masking speech. Testing was administered in the Portable Automated Rapid Testing (PART) application developed by our team; PART facilitates psychoacoustic assessments of auditory processing. (2) Methods: Forty-one individuals (average age 51 years), completed assessments of sensitivity to temporal fine structure (TFS) and spectrotemporal modulation (STM) detection via an iPad running the PART application. Statistical models were used to evaluate the strength of associations between performance on the auditory processing tasks and speech understanding in competition. Age and pure-tone-average (PTA) were also included as potential predictors. (3) Results: The model providing the best fit also included age and a measure of diotic frequency modulation (FM) detection but none of the other potential predictors. However, even the best fitting models accounted for 31% or less of the variance, supporting work suggesting that other variables (e.g., cognitive processing abilities) also contribute significantly to speech understanding in noise. (4) Conclusions: The results of the current study do not provide strong support for previous suggestions that suprathreshold processing abilities alone can be used to explain difficulties in speech understanding in competition among older adults. This discrepancy could be due to the speech tests used, the listeners tested, or the suprathreshold tests chosen. Future work with larger numbers of participants is warranted, including a range of cognitive tests and additional assessments of suprathreshold auditory processing abilities.

Does the Speech Cue Profile Affect Response to Amplitude Envelope Distortion?

Purpose A broad area of interest to our group is to understand the consequences of the "cue profile" (a measure of how well a listener can utilize audible temporal and/or spectral cues for listening scenarios in which a subset of cues is distorted. The study goal was to determine if listeners whose cue profile indicated that they primarily used temporal cues for recognition would respond differently to speech-envelope distortion than listeners who utilized both spectral and temporal cues. Method Twenty-five adults with sensorineural hearing loss participated in the study. The listener's cue profile was measured by analyzing identification patterns for a set of synthetic syllables in which envelope rise time and formant transitions were varied. A linear discriminant analysis quantified the relative contributions of spectral and temporal cues to identification patterns. Low-context sentences in noise were processed with time compression, wide-dynamic range compression, or a combination of time compression and wide-dynamic range compression to create a range of speech-envelope distortions. An acoustic metric, a modified version of the Spectral Correlation Index, was calculated to quantify envelope distortion. Results A binomial generalized linear mixed-effects model indicated that envelope distortion, the cue profile, the interaction between envelope distortion and the cue profile, and the pure-tone average were significant predictors of sentence recognition. Conclusions The listeners with good perception of spectro-temporal contrasts were more resilient to the detrimental effects of envelope compression than listeners who used temporal cues to a greater extent. The cue profile may provide information about individual listening that can direct choice of hearing aid parameters, especially those parameters that affect the speech envelope.

Contributions to Speech-Cue Weighting in Older Adults With Impaired Hearing

Purpose In a previous paper (Souza, Wright, Blackburn, Tatman, & Gallun, 2015), we explored the extent to which individuals with sensorineural hearing loss used different cues for speech identification when multiple cues were available. Specifically, some listeners placed the greatest weight on spectral cues (spectral shape and/or formant transition), whereas others relied on the temporal envelope. In the current study, we aimed to determine whether listeners who relied on temporal envelope did so because they were unable to discriminate the formant information at a level sufficient to use it for identification and the extent to which a brief discrimination test could predict cue weighting patterns. Method Participants were 30 older adults with bilateral sensorineural hearing loss. The first task was to label synthetic speech tokens based on the combined percept of temporal envelope rise time and formant transitions. An individual profile was derived from linear discriminant analysis of the identification responses. The second task was to discriminate differences in either temporal envelope rise time or formant transitions. The third task was to discriminate spectrotemporal modulation in a nonspeech stimulus. Results All listeners were able to discriminate temporal envelope rise time at levels sufficient for the identification task. There was wide variability in the ability to discriminate formant transitions, and that ability predicted approximately one third of the variance in the identification task. There was no relationship between performance in the identification task and either amount of hearing loss or ability to discriminate nonspeech spectrotemporal modulation. Conclusions The data suggest that listeners who rely to a greater extent on temporal cues lack the ability to discriminate fine-grained spectral information. The fact that the amount of hearing loss was not associated with the cue profile underscores the need to characterize individual abilities in a more nuanced way than can be captured by the pure-tone audiogram.