Effects of Amplitude Compression upon Speech Perception: A Review of Research

Abstract

This literature review focuses on two topics: First, the basic types of compression amplifiers are discussed with an emphasis on the primary features affecting the performance characteristics of compression amplitude controlling devices. Second, an historical review is presented of the application of amplitude compression for the hearing impaired with special emphasis on studies concerning the effects of compression amplifiers upon speech perception. Beginning in the 1940's, a few of the studies found substantial benefit to intelligibility with compression compared to no compression; others found only minimal or no improvement in speech perception with amplitude compression. Most of the investigations reported used limiter circuits; whereas, compression circuitry was employed in only two (recent) studies. Most research reported to date has been with prototype desk model units; few studies have actually used hearing aids. Almost all of the research has been with standard monosyllabic word lists with the li...