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

Abstract

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.

High Ripple-Density Resolution for Discriminating Between Rippled and Nonrippled Signals: Effect of Temporal Processing or Combination Products?

“…Given the finding that combination products do not determine the ripple-density resolution, there is a more realistic hypothesis that explains the task-dependent difference in resolutions by different degrees of involvement of the excitation-pattern and temporal-processing mechanisms of frequency analysis, as has been suggested previously (Anderson et al, 2012;Milekhina et al, 2019;Nechaev et al, 2019).…”

“…The hypothesis of temporal processing as a cause of the higher ripple-density resolution for discriminating between a rippled and nonrippled signal has been supported by data on the dependence of resolution on signal center frequency ( Milekhina et al., 2019 ) and ripple depth ( Supin et al., 2019 ). For discrimination between two rippled signals, the dependencies that were found were consistent with the excitation-pattern mechanism; for discrimination between a rippled and nonrippled signal, the dependencies that were found were consistent with the temporal-processing mechanism.…”

“…(2012) , 26.1 ripples/oct by Nechaev et al. (2019) , and 34.2 ripples/oct by Milekhina et al. (2019) .…”

“…Quite different results were obtained when a rippled test signal had to be discriminated from a nonrippled reference signal. Such discrimination was possible at very high ripple densities: up to 60 ripples/oct by Anderson et al (2012), 26.1 ripples/oct by Nechaev et al (2019), and 34.2 ripples/oct by Milekhina et al (2019). Despite the disagreement in estimates of ripple-density resolution (from 26.1 to 60 ripples/oct), a common result of the mentioned studies was that the resolution assessed by discrimination between a rippled and nonrippled signal was several times as high as that assessed by discrimination between two rippled signals of equal ripple densities but different ripple phase patterns.…”

Ripple density resolution dependence on ripple width

“…When the resolution was assessed by distinguishing two rippled stimuli with equal ripple densities but different ripple phases, the resolution was less than 10 ripples/oct [6,7]. When the resolution was assessed by distinguishing between a rippled stimulus and a non-rippled stimulus, it was several times higher: nearly 60 ripples/oct [11], 26 ripples/oct [13], or more than 34 ripples/oct [14]. However, the influence of the ripple width on the ripple density resolution was not investigated in these studies.…”