INTELLIGIBILITY OF CONVERSATIONAL AND CLEAR SPEECH IN NOISE AND REVERBERATION FOR LISTENERS WITH NORMAL AND IMPAIRED HEARING

The effect of articulating clearly on speech intelligibility is analyz ed for ten normal-hearing and two hearing-impaired listeners in noisy, reverberant, and combined environments. Clear speech is more intellig ible than conversational speech for each listener in every environment . The difference in intelligibility due to speaking style increases as noise and/or reverberation increase. The average difference in intell igibility is 20 percentage points for the normal-hearing listeners and 26 percentage points for the hearing-impaired listeners. Two predicto rs of intelligibility are used to quantify the environmental degradati ons: The articulation index (AI) and the speech transmission index (ST I). Both are shown to predict, reliably, performance levels within a s peaking style for normal-hearing listeners. The AI is unable to repres ent the reduction in intelligibility scores due to reverberation for t he hearing-impaired listeners. Neither predictor can account for the d ifference in intelligibility due to speaking style.