Rippled-spectrum resolution dependence on frequency: Estimates obtained by discrimination from rippled and nonrippled reference signals.

The resolution of spectral ripples is a useful test for the spectral resolution of hearing. However, the use of different measurement paradigms might yield diverging results because of a paradigm-dependent contribution of excitation-pattern and temporal-processing mechanisms. In the present study, ripple-density resolution was measured in normal-hearing listeners for several frequency bands (centered at 0.5, 1, 2, and 4 kHz), using two paradigms: (i) discrimination of a rippled-spectrum test signal from a rippled reference signal differing by the ripple phase pattern, and (ii) discrimination of a rippled-spectrum test signal from a nonrippled reference signal. For the rippled reference signals, the resolution slightly depended on signal frequency. For the nonrippled reference signals, the resolution depended on the signal frequency; it varied from 8.8 ripples/oct at 0.5 kHz to 34.2 ripples/oct at 4 kHz. Excitation-pattern and temporal-processing models of spectral analysis were considered. Predictions of the excitation-pattern model agreed with the data obtained with the rippled reference signals. In contrast, predictions of the temporal-processing model agreed with the data obtained with the nonrippled reference signals. Thus, depending on the used reference signal type, the ripple-density resolution estimates characterize the discrimination abilities of the corresponding mechanisms.