Binaural detection performance using reproductible stimuli
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Abstract
A listener's sensitivity to the presence of a sinusoidal target, masked by a sample of random noise, is known to depend on the specific noise sample for both monaural and binaural detection [Gilkey, Robinson, and Hanna, J. Acoust. Soc. Am. 78:1207-1219, 1985]. This work explores to what extent existing quantitative models for binaural detection can predict the sample-by-sample variation observed in listeners' responses. Responses of five subjects for the binaural detection of a 500-Hz, 300-msec, interaurally out-of-phase tone masked by statistically independent samples of narrowband, interaurally-identical noise are reported. A set of 30 noise samples were taken from a noise process with a power spectrum that is 115-Hz wide, centered at 500 Hz. The rms noise pressure is 75 dB SPL. For each subject, the responses show good self-consistency and a strong dependence on individual noise samples (intrasubject correlation coefficients higher than 0.72, typically 0.85). However, there are significant differences between subjects in the pattern of responses across the set of masker samples (intersubject correlation coefficients no higher than 0.7). Subjects' performance values for individual noise samples are compared to the predictions of psychophysical models for binaural detection. Some classes of previously
suggested models have predictions that are not consistent with observed performance. Specifically, sample-level predictions of models for which the decision variable is dominated by the energy in the particular noise sample have no significant correlation with the patterns of responses across noise samples for any subject. In contrast, models that are based on variability of the ITD and/ or IID have predictions that are statistically significantly correlated with most subjects' responses (but no correlation coefficients larger than 0. 7). Black-box models in this class include those with decisions based on the sum of the squares of the ITDs and IIDs, or on the peak-deviations of the ITDs. Results for a physiological model of the dependence of firing patterns of the principal cells in the medial superior olive on ITDs suggest a mechanism that is analogous to black-box models with decision variables based on the variability of the ITD.
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This work is being made available in OpenBU by permission of its author, and is available for research purposes only. All rights are reserved to the author.