Rippled Depth Thresholds: Estimates Obtained by Discrimination From Rippled and Nonrippled Reference Signals

The objective of the study was to better understand of contribution of excitation-pattern and temporal-processing mechanisms of frequency analysis to discrimination of complex-spectrum signals in various discrimination tasks. Using rippled-spectrum signals, the ripple depth thresholds were measured as functions of ripple density under conditions of rippled or non-rippled reference signals. With rippled reference signals, the ripple depth thresholds were as low as 0.11 at low ripple densities (2–3 cycles/oct) and rose to 1.0 at a ripple density of 8.9 cycles/oct. For non-rippled reference signals, ripple depth thresholds were nearly the same as for rippled reference signals at ripple densities of up to 7 cycles/oct; at ripple densities of 10 cycles/oct and higher, ripple depth thresholds rose slowly and reached 1.0 at a ripple density of 26 cycles/oct. The results hypothetically suggest contributions of the excitation-pattern processing and temporal-processing mechanisms of frequency analysis to discrimination of rippled signals. The excitation-pattern mechanism featured low depth thresholds at low ripple densities but could not function at ripple densities above 10 cycles/oct. The temporal-processing mechanism manifested at higher ripple densities and non-rippled reference stimuli.