Jean C. Krause
Louis D. Braida
MIT, Cambridge, MA 02139
In adverse listening conditions, large and robust increases in intelligibility can be achieved by speaking clearly. The most striking differences between clear and conversational speech are associated with differences in speaking rate. To understand these differences, the intelligibility of speech in a variety of speaking modes was investigated at three different speaking rates. Talkers with significant speaking experience were asked to produce clear and conversational speech at slow, conversational, and quick rates. Previous studies show that the speaking rate for clear speech is roughly one-half that of conversational speech. Therefore, during training, the talkers were given feedback on their intelligibility in order to elicit the clearest possible speech at conversational and quick speaking rates. Talkers also recorded sentences in several other speaking modes such as soft, loud, and conversational with pauses inserted, as required for input to some automatic speech recognition systems. All speech materials recorded were nonsense sentences which provide no semantic context to aid listeners in identifying key words. The effects of changes in speaking rate on intelligibility of various speaking modes for normal hearing listeners in a background of wideband noise are discussed. [Work supported by NIH.]