Effects of Signal Distortion on Three Listener Performance Tasks

Abstract

The purpose of the study was to assess the usefulness of three listener performance tasks: learning rate, recall, and listener confidence ratings, as criteria for evaluating speech communication systems by determining if performance on the three tasks varied systematically with type and severity of speech-signal distortion. Lists of 24 words, equal in intelligibility and content but differing in acoustical distortion, were presented auditorily to five groups of 20 listeners. Results showed that learning rate decreased as the amount of distortion associated with the speech signal increased. Listeners were more confident of correct reception of the words as the signal distortion decreased and were more confident of the incorrect reception as the distortion increased. There were no differences in the number of words correctly recalled between the five distortion conditions. It is suggested that the intelligibility score alone is limited in its ability to assess the transmission capabilities of a speech-communication system and that learning rate and listener confidence ratings may provide additional information useful in evaluating speech-communication systems.