Estimating listeners' internal noise from intensity and spectral-shape discrimination tasks

Abstract

Within the framework of signal-detection theory, listeners' ability to process stimulus information is partly limited by their internal noise. Knowing the internal noise of listeners will allow the researcher to predict their performance in various detection or discrimination tasks. For the purpose of estimating internal noise, in this study we measure the ability of listeners to discriminate the intensities of pure tones (Exp. 1) and two-tone complexes (Exp. 2), and to discriminate the spectral shapes of two-tone complexes (Exp. 3). The results from five listeners were fitted with an internal-noise model. The analysis showed that a major portion of the internal noise is correlated across frequency channels. This outcome is consistent with the conclusions of previous studies that estimated internal noise using different methods. Under the dominance of channel-correlated internal noise over channel-specific internal noise, listeners' ability to integrate information over frequency should be reduced, and their performance in detection and discrimination should be less affected by uncertainty for the signal parameters.