Intelligibility of Natural and Distorted Speech Led through Ten Hearing Aids to Normal and to Deafened Individuals

Abstract

Three female and two male voices were taped reading sentences which were re-recorded after being led through ten hearing aids with electroacoustic characteristics ranging from very good to poor. Normal ears and ears with varying types and degree of deafness were used. A latin square design assured proper comparisons among aids. Each listener repeated 100 colloquial sentences which were taped under a natural speaking condition, 100 under a nasal-plus-speeded condition, and 100 under an interrupted speech condition. Comparisons of normal and deafened groups in terms of percentage of words correctly understood show that the deafened group always did poorer even though corrective amplification was used. In most cases the hearing aids were ranked in similar orders by both groups within a speech category, but were ranked differently from the natural voice condition to the distorted conditions, especially by normals. The data have also been analyzed in terms of the minimum number of voices and types of speech distortion necessary to provide an adequate test battery for such purposes. Comparisons have been made between performance on each aid versus the many electroacoustic characteristics known for each aid. (This research is supported in part by the Office of Vocational Rehabilitation.)