Temporal and spectral processing in increment detection

Abstract

Increment detection for narrow-band noise can be enhanced by adding flanking noise bands remote in frequency. With flanking bands present, spectral analyses reveal the increment to produce a change in spectral shape and temporal analyses correspondingly reveal an increase in the envelope amplitude of the incremented band. This experiment was designed to identify the auditory cue(s), temporal or spectral, underlying increment detection with flanking bands. Performance was compared for random noises, having pronounced envelope fluctuations, and low-noise noises, having minimal envelope fluctuations. All noises were 10-Hz wide. The incremented band, centered at 2500 Hz, was presented either alone or with four flanking bands (1500, 2000, 3000, and 3500 Hz). The five noises had either coherent or incoherent temporal envelopes. Conditions having a ±10-dB within-trial random level variation were also included. Coherent flanking bands always facilitated increment detection for random but not low-noise noise, suggesting a temporal rather than a spectral basis for the improved detection. With the random level variation, thresholds were lower for incoherent than single-band conditions, suggesting the use of spectral shape cues. [Research supported by NIH.]