Ripple Glide Direction Discrimination and Its Relationship to Frequency Selectivity Estimated Using Notched Noise

Experiment 1 evaluated a test of spectral resolution, denoted STRtdir, which estimates the highest ripple density at which stimuli with upward- and downward-gliding spectral ripples can be discriminated. The test was intended to avoid the confounding cues that can occur for other tests using similar stimuli. Mean thresholds for seventeen normal-hearing participants were similar to those obtained by Narne et al. [1] for the discrimination of static spectral ripples and for the discrimination of dynamic spectral ripples with the spectral edges masked by noise. Experiment 2 assessed whether performance on the STRtdir depended on "local" or "global" frequency selectivity. Participants with both normal and impaired hearing were tested using the STRtdir, and their auditory filter shapes were estimated using the notched-noise method for centre frequencies of 0.5, 1, 2, and 4 kHz. The individual STRtdir thresholds were predicted more accurately using a "local" excitation-pattern model, based on the assumption that the threshold is reached when the peak-to-valley ratio (PVR) in the excitation pattern in any one-octave wide frequency region reaches a criterion value, than by a "global" model based on the assumption that threshold is determined by the average PVR across the whole excitation pattern.