Combinations of Amplitude and Frequency Differences in Auditory Discrimination

Several versions of a neural excitation pattern model of the peripheral auditory system lead to the implication that simultaneous amplitude and frequency discriminations should exhibit strong interactions in the presence of bandlimited masking noise. Several previous studies used signals simultaneously modulated in amplitude and frequency. Subjects were required to match two dissimilar sounds, and the results followed the predicted amplitudefrequency interactions. Calculations of the spectra of these modulated signals, and actual measurements in the laboratory, suggest a very simple interpretation of the data based on spectral similarity. We report the results of discrimination experiments which used unmodulated tones and bandlimited “maskers”, and which also should have revealed the predicted interactions. These interactions were not found, and we, therefore, conclude that the simple excitation pattern models need to be revised.