Effects of audibility and multichannel wide dynamic range compression on consonant recognition for listeners with severe hearing loss

Authors

Evelyn Davies-Venn, University of WashingtonFollow
Pamela Souza, University of Washington
Marc Brennan, University of WashingtonFollow
G. Christopher Stecker, University of Washington

Document Type

Article

Date of this Version

2009

Citation

Ear Hear. 2009 October; 30(5): 494–504

Comments

Copyright 2009 by Lippincott Williams & Wilkins

NIH Public Access

doi:10.1097/AUD.0b013e3181aec5bc

Abstract

Objective—This study examined the effects of multichannel wide-dynamic range compression (WDRC) amplification and stimulus audibility on consonant recognition and error patterns.

Design—Listeners had either severe or mild-to-moderate sensorineural hearing loss. Each listener was monaurally fit with a wearable hearing aid using typical clinical procedures, frequency-gain parameters and a hybrid of clinically prescribed compression ratios for DSL (Scollie et al., 2005) and NAL-NL (Dillon, 1999). Consonant-vowel nonsense syllables were presented in soundfield at multiple input levels (50, 65, 80 dB SPL). Test conditions were four-channel fast-acting WDRC amplification and a control compression limiting (CL) amplification condition. Listeners identified the stimulus heard from choices presented on an on-screen display. A between-subject repeated measures design was used to evaluate consonant recognition and consonant confusion patterns.

Results—Fast-acting WDRC provided a considerable audibility advantage at 50 dB SPL, especially for listeners with severe hearing loss. Listeners with mild-to-moderate hearing loss received less audibility improvement from the fast-acting WDRC amplification, for conversational and high level speech, compared to listeners with severe hearing loss. Analysis of WDRC benefit scores revealed that listeners had slightly lower scores with fast-acting WDRC amplification (relative to CL) when WDRC provided minimal improvement in audibility. The negative effect was greater for listeners with mild-to-moderate hearing loss compared to their counterparts with severe hearing loss.

Conclusions—All listeners, but particularly the severe loss group, benefited from fast-acting WDRC amplification for low-level speech. For conversational and higher speech levels (i.e., when WDRC does not confer a significant audibility advantage), fast-acting WDRC amplification appears to slightly degrade performance. Listeners’ consonant confusion patterns suggest that this negative effect may be partly due to fast-acting WDRC-induced distortions which alter specific consonant features. In support of this view, audibility accounted for a greater percentage of the variance in listeners’ performance with CL amplification compared to fast-acting WDRC amplification.