A Model of the "effective" signal processing in the auditory system
by Torsten Dau, Dirk Püschel and Armin Kohlrausch
This document contains the two abstracts of the accepted JASA
papers (in press)
(Part I : Model structure)
This paper describes a quantitative model for signal processing in the
auditory system. The model combines a series of preprocessing stages
with an optimal detector as the decision device. The present paper
gives a description of the various preprocessing stages and of the
implementation of the optimal detector. The output of the
preprocessing stages is a time-varying activity pattern to which
`internal noise' is added. In the decision process a stored temporal
representation of the signal to be detected (template) is compared
with the actual activity pattern. The comparison amounts to
calculating the cross correlation between the two temporal patterns
and is comparable to a `matched filtering' process. The detector
itself derives the template at the beginning of each simulated
threshold measurement from a supra-threshold value of the
stimulus. The model allows the use of the same signals and threshold
procedures as in actual experiments. In the accompanying paper [Dau
et al., J. Acoust. Soc. Am. (1996)] data obtained for human observers
are compared with the optimal-detector model for various masking
conditions.
(Part II : Measurements and Simulations)
This and the accompanying paper [Dau et al., J. Acoust. Soc. Am.
(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 3-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
running-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.
torsten@medi.physik.uni-oldenburg.de
Last modified:
Tue Mar 19 12:20:36 1996