EVALUATION OF THE EFFECT OF SPEECH-RATE SLOWING ON SPEECH-INTELLIGIBILITY IN NOISE USING A SIMULATION OF COCHLEAR HEARING-LOSS

The effect of digital processing, which slows the speed of speech (spe ech-rate) without changing its pitch, has been examined. The processin g is intended to make speech communication easier by allowing more tim e for cognitive processing when the listening situation is difficult, for example, when listening to a foreign language, or when the user ha s a hearing loss. The speech-rate slowing makes use of a pitch-synchro nous partial expansion of the waveform in the time domain. The process ing was evaluated using a simulation of hearing loss which has been sh own to lead to reduced intelligibility for normally, hearing subjects. The simulation included the major consequences of cochlear hearing lo ss; loudness recruitment, threshold elevation, and reduced frequency s electivity. Two simulations were used: a moderate flat hearing loss wi th auditory filters broadened by a constant factor of three (B3R2); an d the same loss with linear amplification applied prior to the simulat ion processing (B3R2+). Two expansion rates were used for the speech-r ate slowing, 1.25 and 1.50. The intelligibility of sentences in speech -shaped noise was measured. For both simulation conditions, the speech -rate slowing did not give any improvement in intelligibility. Rather, in condition B3R2+ the slowing produced statistically significant del eterious effects on intelligibility. The results suggest that artifici al speech-rate slowing will not improve the intelligibility of speech in noise for hearing-impaired people who have the type of cochlear dam age simulated in this test. (C) 1998 Acoustical Society of America.