In normal-hearing listeners, thresholds of spectral ripple depth were measured as a function of ripple density. The test
signal had a rippled spectrum with ripple phase reversals very 400 ms. The reference signal has either a rippled
spectrum with constant ripple phase or had a flat (non-rippled) spectrum. Each measurement trial included one test and
two reference signals, randomly alternated. The goal of the listener was to identify the test signal that differed from
the two other (reference) signals. With a rippled-spectrum reference signal, the threshold of spectral ripple depth was
0.11 (dimensionless units) at low ripple densities of 2–3 ripples/oct; the threshold increased with increasing the
ripple density and reached the maximum possible value of 1.0 at a density of 8.9 ripples/oct. With a flat-spectrum
reference signal, thresholds were nearly the same as for the rippled-spectrum reference signals at ripple densities up
to 7 ripples/oct; however, for the flat-spectrum reference signals, threshold rise got slower at higher ripple
densities, and trached the maximum possible value of 1.0 at a density of 26 ripples/oct. It is suggested that the
difference between results obtained with different reference signals originated from different contributions of the
spectral and temporal mechanisms of frequency analysis. At lower ripple densities, discrimination both between two
rippled spectra and between rippled and flat spectra proceeds mostly basing on the spectral-processing frequency-
discrimination mechanism, whereas at higher ripple densities discrimination between rippled and flat spectra involves
the temporal-processing mechanism.
hearing, rippled spectrum, resolution
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