Multi-Channel Compression and Speech Intelligibility in Industrial Noise

Abstract

This study examined how various forms of compression affect speech intelligibility in moderately high levels of industrial noise. Thirteen listeners with high-frequency sensorineural hearing loss were fit with a digital hearing aid programmed to operate in three modes of compression: compression limiting, compression of low frequencies only (BILL), and compression of high frequencies only (TILL). For each of these conditions, listeners attempted to recognize CID W-22 monosyllabic words delivered in a background of recorded industrial noise. Word recognition was also measured in quiet for the compression-limiting condition. The highest word identification scores were obtained in quiet (80.9%). Of the three conditions in which background noise was present, the mean score was highest for TILL compression (52.4%), and lowest for BILL (39.7%). Representative time-weighted average (TWA) exposures for each of the aided noise conditions were determined by means of a procedure outlined previously by the first author. The projected 8-hour amplified TWA with the hearing aid programmed to the TILL configuration was 94 dBA, whereas TWAs for the linear and BILL configurations were each 104 dBA. Thus, the highest intelligibility and lowest noise exposures were obtained with the aid in the TILL mode.