A quantitative model of the "effective" signal processing in the auditory system. II. Simulations and measurements.

This and the accompanying paper [Dau et al., J. Acoust. Soc. Am. 99, 3615-3622 (1996)] describe a quantitative model for signal processing in the auditory system. The model combines several stages of preprocessing with a decision device that has the properties of an optimal detector. The present paper compares model predictions for a variety of experimental conditions with the performance of human observers. Simulated and psychophysically determined thresholds were estimated with a three-interval forced-choice adaptive procedure. All model parameters were kept constant for all simulations discussed in this paper. For frozen-noise maskers, the effects of the following stimulus parameters were examined: signal frequency, signal phase, temporal position and duration of the signal within the masker under conditions of simultaneous masking, masker level, and masker duration under conditions of forward masking, and backward masking. The influence of signal phase and the temporal position of the signal, including positions at masker onset, was determined for a random-noise masker and compared with corresponding results obtained for a frozen noise. The model describes all the experimental data with an accuracy of a few dB with the following exceptions: forward-masked thresholds obtained with brief maskers are too high and the change in threshold with a change in signal duration is too small. Both discrepancies have their origin in the adaptation stages in the preprocessing part of the model. On the basis of the wide range of simulated conditions we conclude that the present model is a successful approach to describing the detection process in the human auditory system.