PURPOSE: To investigate the effect of modulation rate on masking release for speech. METHODS:Fifteen normal hearing subjects participated in the study. They were tested on speech perception in noise using the sentences of the HINT-Brazil. Speech recognition thresholds were obtained in the presence of steady masking and amplitude modulated masking at rates of 4, 8, 16, 32 and 64 Hz. The magnitude of masking release was obtained for each modulation rate, and results were compared. RESULTS:Data showed significantly lower speech thresholds when the masking noise was amplitude modulated at rates of 4, 8, 16 and 32 Hz, when compared to thresholds obtained in steady noise or noise modulated at 64 Hz. Speech-to-masker ratios (SMR) were higher in steady masking noise, followed by modulated noise at 64 Hz, and lower for modulated rates of 32, 16, 8 and 4 Hz, respectively. CONCLUSION: The magnitude of masking release for speech does not seem to differ significantly among modulation rates of 4 to 32 Hz. However, for a modulation rate of 64 Hz the magnitude of masking release is significantly reduced.
Hearing; Perceptual masking; Speech perception; Speech discrimination tests; Noise