We possess a remarkable ability to 'hear out'(segregate) the individual sound sources that makeup the complex, acoustic environments we encounter in everyday listening. Understanding this ability has been a preoccupation of psychoacoustic research, but it is a tremendous challenge. Perturbation analysis is a methodological approach that has advanced understanding of related problems in vision [Murray, R.F. 2011. J. of Vision 11, 1-25]. Here the approach is adapted to audition. The application proceeds in three stages: First, simple speech and environmental sounds are synthesized according to a generative model of the sound-producing source. Second, listener decision strategy in segregating a target from non-target (noise) source is determined from decision weights (regression coefficients) relating listener judgments regarding the target to lawful perturbations in acoustic parameters, as dictated by the generative model. Third, factors limiting segregation are identified by comparing the obtained weights and residuals to those of a maximum- likelihood (ML) observer that optimizes segregation based on the equations of motion of the generating source. The approach represents a significant advance over traditional methods that infer listener decision strategy from performance accuracy or from the effect of placing acoustic cues in unlawful opposition.
Specific aims are to apply this method to (1) test between two major classes of segregation models, target enhancement vs. noise cancellation, (2) test predictions of acoustics-based versus mechanics-based hypotheses regarding source segregation, common fate vs. common source, (3) quantify the relative influence of target-noise uncertainty and similarity, (4) determine the influence of level dominance on sound source segregation, and (5) account for diverse patterns of behavior across tasks by using the decision weights to identify individual listening styles. It is expected that the knowledge gained from these studies will inform research on broader aspects of the problem of sound source segregation, including those relevant to the evaluation and treatment of disordered hearing as it impacts everyday listening in noisy environments.
By advancing our understanding of the normal processes underlying sound source segregation the results may prove key in the development of technologies and rehabilitative strategies that deal more effectively with the impact of dysfunctional hearing on everyday listening.
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