Julius L. Goldstein
Central Inst. for the Deaf, 818 South Euclid Ave., St. Louis, MO 63110
Classical energy-detection theory [Green and Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966)] predicts that masking of tones by Gaussian noise is limited by the variability of detector responses and by internal auditory noise. It elegantly relates detection variability to masker duration--bandwidth product (TW). The theory accounts reasonably for Gaussian maskers with fixed RMS levels, but fails when the level is randomly roved with each stimulus presentation, suggesting that the auditory system detects waveform cues. A solution to this problem is proposed in which energy detection is replaced with the dual cues of envelope peak detection and normalized envelope peak detection, which are optimally processed as in classical theory [Goldstein and Hall, J. Acoust. Soc. Am. 97, 3330(A) (1995)]. The model was studied with periodic noise maskers comprising successive harmonics having uniform amplitudes and random phases, and with Gaussian noise maskers. Fixed-level masked threshold predictions converge to ~-4 dB SNR for both noises when TW>4, with small differences otherwise. Roved-level predictions for the periodic noise masker (one period duration) are ~5 dB higher. Agreement exists between model predictions and the systematic masking data of Richards [J. Acoust. Soc. Am. 91, 3424--3435 (1992)].