Influence of high pass filtering on the intelligibility of amplitude-compressed speech.

Monosyllabic triplet word intelligibility scores were obtained from normal-hearing and hearing-impaired, loudness-recruiting subjects under two experimental conditions: (1) high-pass (1200 Hz)-filtered, linear amplification, and (2) high-pass (1200 Hz)-filtered, compression amplification using input-to-output ratios of 5:1 and 20:1. Test materials were administered at increased sensation levels of 0, 10, 20, and 30 dB. In general, speech intelligibility was slightly enhanced for normal and hearing-impaired listeners, but only at lower sensation levels. Moreover, the improvement was observed only under the filtered, compression amplification condition for both groups. No important differences were observed between the two compression ratios used. This compression advantage may or may not be observed in clinical hearing aid evaluations.