MASKING OF SPEECH BY AMPLITUDE-MODULATED NOISE

The degree of masking of human speech by environmental noise may be influenced by amplitude variations in the noise. The listener's condition with respect to age and auditory function may affect his sensitivity to such noise. Also, fatigue effects are possible after prolonged exposure to masking noise. These aspects have been tested in the present study. The results show that in general, amplitude modulation of a masking noise reduces its speech masking effect as compared to unmodulated noise of the same r.m.s. sound level and spectrum. Age did not affect the release of masking found in AM noise. However, hearing-impaired listeners obtained much less release of speech masking than those with normal hearing. Small but statistically significant fatigue effects were found after up to 60 min exposure to noise at 60 dB SPL. The speech-to-noise ratio needed for 30% correct speech recognition was significantly affected by both age and hearing loss. © 1991.