Physical measurements of the transfer function from a free−field sound source to a microphone in the subject’s ear canal indicate that there are two independent localization cues generated by the pinna. For sound sources in the vertical median plane, there is a systematic change in the frequency response as a function of elevation angle, and a disparity between the left−ear and right−ear responses which also changes systematically with elevation angle. Independent psychophysical measurements indicate that these pinna cues are detectable by subjects, and both are used by subjects in vertical localization tasks. Subject Classification: 65.62, 65.75.

A mathematical model based on statistical decision theory has been devised to represent the human auditory localization task. The known localization cues have been represented as Gaussian random variables, so that their interaction in a given experiment can be analyzed (and predicted) along the lines of classical detection/estimation theory. We have applied this technique to most of the horizontal and vertical localization experiments reported in the literature during the past ten years, encompassing over 200 subjects and 20000 trials. Using a nonlinear regression program we have been able to estimate the standard deviations of four of the auditory localization cues, allowing objective comparison of their relative accuracy. The resulting model provides a relatively good fit to the published results on 40 localization experiments. Subject Classification: [43]65.62, [43]65.35, [43]65.58. LIST OF SYMBOLS (C•S) •' m M N P,(m) decision criteria speaker sp•cing number of responses in error by m speakers span-dependent component of (• index on sound sources index on cues index on response error number of experiments number of trials in a given experiment number of sound sources probability of response in error by m speakers

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