Relating hearing loss and executive functions to hearing aid users' preference for, and speech recognition with, different combinations of binaural noise reduction and microphone directionality.

Tobias Neher

doi:10.3389/fnins.2014.00391

Abstract

Knowledge of how executive functions relate to preferred hearing aid (HA) processing is sparse and seemingly inconsistent with related knowledge for speech recognition outcomes. This study thus aimed to find out if (1) performance on a measure of reading span (RS) is related to preferred binaural noise reduction (NR) strength, (2) similar relations exist for two different, non-verbal measures of executive function, (3) pure-tone average hearing loss (PTA), signal-to-noise ratio (SNR), and microphone directionality (DIR) also influence preferred NR strength, and (4) preference and speech recognition outcomes are similar. Sixty elderly HA users took part. Six HA conditions consisting of omnidirectional or cardioid microphones followed by inactive, moderate, or strong binaural NR as well as linear amplification were tested. Outcome was assessed at fixed SNRs using headphone simulations of a frontal target talker in a busy cafeteria. Analyses showed positive effects of active NR and DIR on preference, and negative and positive effects of, respectively, strong NR and DIR on speech recognition. Also, while moderate NR was the most preferred NR setting overall, preference for strong NR increased with SNR. No relation between RS and preference was found. However, larger PTA was related to weaker preference for inactive NR and stronger preference for strong NR for both microphone modes. Equivalent (but weaker) relations between worse performance on one non-verbal measure of executive function and the HA conditions without DIR were found. For speech recognition, there were relations between HA condition, PTA, and RS, but their pattern differed from that for preference. Altogether, these results indicate that, while moderate NR works well in general, a notable proportion of HA users prefer stronger NR. Furthermore, PTA and executive functions can account for some of the variability in preference for, and speech recognition with, different binaural NR and DIR settings.

Highlights

Substantial variability in outcome is a consistent finding in hearing aid (HA) research
Based on the results summarized above we hypothesized that (1) poorer reading span (RS) and larger pure-tone average hearing loss (PTA) would be associated with stronger preference for strong noise reduction (NR), (2) RS and the other measures of executive function would be differentially related to preference for HA processing, (3) preference for strong NR would increase with input signal-to-noise ratio (SNR), DIR would reduce the amount of speech distortion and potentially weaken any observed relations between preferred NR strength and the measures of executive function, and (4) the associations between speech recognition, PTA, and the measures of executive function would be different from those for preference
For the “worse RS” subgroup, we found that the decrement in speech recognition due to strong NR was basically unaffected by microphone setting (7.6 vs. 7.0 rationalized arcsine units (RAU)), whereas for the “better RS” subgroup it was slightly larger with the omnidirectional setting (11.2 vs. 7.6 RAU)

Summary

Introduction

Substantial variability in outcome is a consistent finding in hearing aid (HA) research This holds true for a broad range of HA technologies, including amplification (e.g., Gatehouse et al, 2006a,b), noise reduction (NR) processing (e.g., Lunner, 2003; Brons et al, 2013), microphone directionality (DIR; e.g., Ricketts and Mueller, 2000; Keidser et al, 2013), and frequency compression (e.g., Glista et al, 2009; Souza et al, 2013). These studies suggest that HA users with smaller working memory capacity fare better with less aggressive HA processing whereas HA users with larger working memory capacity fare better with more aggressive HA www.frontiersin.org

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