Auditory-filter characteristics derived from direct-masking data and pulsation-threshold data with a rippled-noise masker

The masker was ’’rippled noise,’’with a power spectrum (intensity on a linear frequency scale) shaped according to a sinusoidal function. The test signal was a pure tone. The masking effectiveness of the rippled noise depends on the position of its peaks and troughs relative to the test-tone frequency, but this dependence decreases for high-ripple densities (thus, for ripples with small peak-to-peak distances along the frequency scale). The results of masking experiments as a function of the position and the density of the ripple around the test-tone frequency allow an estimation of the degree of auditory frequency resolution in terms of a filter characteristic. Several masking paradigms were applied: direct masking, forward masking, and pulsation threshold. It was found that the degree of frequency resolution estimated both from pulsation-threshold data and from forward-masking data is substantially higher than that estimated from direct-masking data. The difference is about a factor of two when expressed in terms of the bandwidth of the auditory filter. This difference is interpreted as reflecting spectral sharpening by lateral suppression which apparently manifests itself only in threshold measurements where masker and test tone are presented nonsimultaneously.