A model of auditory image flow. II. Detection of amplitude and frequency modulation
Neil P. McAngus Todd · The Journal of the Acoustical Society of America · 1998
In order to evaluate the cortical model proposed in Todd [these proceedings] it was applied to the phenomenon of modulation detection. It was assumed that a discrimination task involves the correlation of the spatio-temporal power spectra of two image sequences, such as may occur in a typical 2A-2IFC procedure. The correlation was computed by k(1−r), where r is the product moment correlation, for four different modulation frequencies, 4, 16, 64, and 256 Hz at four modulation depths for both AM and FM of a 1000-Hz carrier of 1000-ms duration against the image power spectrum of an unmodulated 1000-Hz 1000-ms tone. The obtained measures were then linearly regressed (with no intercept) as a function of the square of the modulation index. In all cases k(1−r) gave a good fit (R2>0.95) for both AM and FM. For each of the modulation frequencies the slope of the regression could be used to estimate the model thresholds. The model shows the correct behavior for AM and FM detection. This mechanism, it is suggested, may provide an account of modulation detection interference since low spatial-frequency filters span several ERBs.