Multi-channel compression and speech intelligibility in industrial noise

This study examined how various forms of compression affect speech intellig ibility in moderately high levels of industrial noise. Thirteen listeners w ith high-frequency sensorineural hearing loss were fit with a digital heari ng aid programmed to operate in three modes of compression: compression lim iting, 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 recor ded industrial noise. Word recognition was also measured in quiet for the c ompression-limiting condition. The highest word identification scores were obtained in quiet (80.9%). Of the three conditions in which background nois e was present, the mean score was highest for TILL compression (52.4%), and lowest For BILL(39.7%). Representative time-weighted average (TWA) exposur es for each of the aided noise conditions were determined by means of a pro cedure outlined previously by the First author. The projected 8-hour amplif ied TWA with the hearing aid programmed to the TILL configuration was 94 dB A, whereas TWAs for the linear and BILL configurations were each 104 dBA. T hus, the highest intelligibility and lowest noise exposures were obtained w ith the aid in the TILL mode.