Relationship Among Signal Fidelity, Hearing Loss, and Working Memory for Digital Noise Suppression

Abstract

Objectives The present study considered speech modified by additive babble combined with noise-suppression processing. The purpose was to determine the relative importance of the signal modifications, individual peripheral hearing loss, and individual cognitive capacity on speech intelligibility and speech quality. Design The participant group consisted of 31 individuals with moderate high-frequency hearing loss ranging in age from 51 to 89 years (mean= 69.6 years). Speech intelligibility and speech quality were measured using low-context sentences presented in babble at several signal-to-noise ratios. Speech stimuli were processed with a binary mask noise-suppression strategy with systematic manipulations of two parameters (error rate and attenuation values). The cumulative effects of signal modification produced by babble and signal processing were quantified using an envelope-distortion metric. Working memory capacity was assessed with a reading span test. Analysis of variance was used to determine the effects of signal processing parameters on perceptual scores. Hierarchical linear modeling was used to determine the role of degree of hearing loss and working memory capacity in individual listener response to the processed noisy speech. The model also considered improvements in envelope fidelity caused by the binary mask and the degradations to envelope caused by error and noise. Results The participants showed significant benefits in terms of intelligibility scores and quality ratings for noisy speech processed by the ideal binary mask noise-suppression strategy. This benefit was observed across a range of signal-to-noise ratios and persisted when up to a 30% error rate was introduced into the processing. Average intelligibility scores and average quality ratings were well-predicted by an objective metric of envelope fidelity. Degree of hearing loss and working memory capacity were significant factors in explaining individual listener’s intelligibility scores for binary mask processing applied to speech in babble. Degree of hearing loss and working memory capacity did not predict listeners’ quality ratings. Conclusions The results indicate that envelope fidelity is a primary factor in determining the combined effects of noise and binary mask processing for intelligibility and quality of speech presented in babble noise. Degree of hearing loss and working memory capacity are significant factors in explaining variability in listeners’ speech intelligibility scores but not in quality ratings.

Theoretical Issues of Validity in the Measurement of Aided Speech Reception Threshold in Noise for Comparing Nonlinear Hearing Aid Systems

“…The reward for this cost is that one can estimate both the position (SRTn) and slope of the psychometric function. The occurrence of 0% or 100% responses may be regarded as informative, rather than "waste," as it signals a need to look into other domains of outcome [e.g., listening effort (Sarampalis et al, 2009;Zekveld et al 2010), speech quality (Arehart et al, 2015), or cognitive spare capacity (Rudner et al, 2012;Ng et al, 2013)] for pertinent differences between HA systems. It should be noted that speech and noise materials optimized for SRTn measurements (i.e., providing steep psychometric functions) may not be optimally efficient for procedures estimating percent-correct at fixed SNRs (where a shallow psychometric function is more efficient).…”

Directional Processing and Noise Reduction in Hearing Aids: Individual and Situational Influences on Preferred Setting

“…In light of the finding that the additional (noise sensitivity and personality) predictors considered here were ineffective, there remains a need for alternative measures that are better able to capture individual differences in preferred DIR and NR processing. In this context, one candidate could be physical performance measures such as in-situ SNR (or directivity) improvement and target signal fidelity (or distortion) that have previously been found to have some predictive value in HA research (Keidser et al, 2013;Arehart et al, 2015). Currently, it is also unclear if the results we obtained would generalize to other cohorts of HA users or if acclimatization to the different processing conditions would impact outcome.…”

Hearing aid noise suppression and working memory function

“…That is, participants with shorter reading span achieved better recall due to noise suppression for words that occurred towards the end of the sequence of sentences, whereas participants with While the findings of Ng et al speak in favour of a relation between reading span and noise suppression outcome, those of other researchers do not. To illustrate, Arehart et al (2015) tested a group of hearing-impaired listeners in terms of speech recognition and speech quality with the algorithm also used by Ng et al Even though reading span was a significant predictor of overall speech recognition, no interaction with noise suppression outcome was found. Using a dual-task paradigm that combined speech recognition with a visual tracking task, Desjardins & Doherty (2014) investigated the effects of modulation-based noise suppression with a group of HA users.…”