Discrimination of rippled spectra with different ripple densities
Discrimination of rippled-spectrum signals depending on the standard ripple density was studied. The measurements were performed using a tree-alternative forced-choice procedure at signal center frequencies of 1, 2 and 4 kHz. Thresholds of ripple-density difference increased with increasing the standard ripple density. At standard ripple densities of  2 to 10 cycles/oct, thresholds were nearly equal for signal frequencies of 1 to 4 kHz. They were from 0.06 cycle/oct at a standard density of 2 cycle/oct to 5–7 cycle/oct at a standard density of 10 cycle/oct. Signal couldnot be discriminate at standard ripple densities above 10 cycle/oct and signal frequencies of 1 and 2 kHz. At a signal frequency of 4 kHz, signals could be discriminated at standard ripple densities above 20 cycle/oct. Discrimination of signal at a center frequency of 4 kHz and ripple densities above 10 cycle/oct can be explained by temporal processing, whereas discrimination at ripple densities below 10 cycle/oct can be explained by frequency processing.