Comparison of Multichannel Wide Dynamic Range Compression and ChannelFree Processing Strategies on Consonant Recognition

Abstract

Background: Both wide dynamic range compression (WDRC) and ChannelFree (CF) processing strategies in hearing aids were designed to improve listener comfort and consonant identification, yet few studies have actually compared them. Purpose: To determine whether CF processing provides equal or better consonant identification and subjective preference than WDRC. Research Design: A repeated-measures randomized design was used in which each participant identified consonants from prerecorded nonsense vowel–consonant–vowel syllables in three conditions: unaided, aided using CF processing, and aided using WDRC processing. For each of the three conditions, syllables were presented in quiet and in a speech-noise background. Participants were also asked to rate the two processing schemes according to overall preference, preference in quiet and noise, and sound quality. Study Sample: Twenty adults (seven females; mean age 69.7 yr) with ≥1 yr of hearing aid use participated. Ten participants had previous experience wearing aids with WDRC, and 10 had previous experience with CF processing. Participants were tested with both WDRC and CF processing. Data Collection and Analysis: Number of consonants correct were measured and used as the dependent variable in analyses of variance with subsequent post hoc testing. For subjective preference, a listener rating form was employed with subsequent χ2 analysis. Results: Overall results showed that signal-processing strategy did not significantly affect consonant identification or subjective preference, nor did previous hearing aid use influence results. Listeners with audiometric slopes exceeding 11 dB per octave, however, preferred CF processing and performed better in noise with CF processing. Conclusion: CF processing is a viable alternative to WDRC for listeners with more severely sloping audiometric contours.