ASA 127th Meeting M.I.T. 1994 June 6-10

4aPP24. Temporal integration, multiple looks, and signal uncertainty.

Gregory H. Wakefield

Dept. of Elec. Eng. and Comput. Sci., 1301 Beal Ave., Univ. of Michigan, Ann Arbor, MI 48109

Viemeister and Wakefield [J. Acoust. Soc. Am. 90, 858--865 (1991)] presented experimental results that challenged the notion of temporal integration as some form of decision process characterized by a long time constant. When the signal consists of brief temporal pulses, detection thresholds vary with the square root of duration, which is consistent with a multiple-look observer. However, when the signal is a continuous sinusoid, detection thresholds vary linearly with duration. The present paper introduces a multiple-look observer in which signal uncertainty and sequential estimation are incorporated. The general form of this observer involves a sequential refinement of the alternative and null hypotheses (from highly uncertain to highly certain stimulus conditions) during the observation interval. Several simplifying assumptions yield an ideal observer whose performance, which can be evaluated analytically, predicts the form of temporal integration for a variety of signals including sinusoids, wideband noise, and pulse sequences. The generality of the theoretical results and experimental verification of the sequential nature of the observer are discussed. [Work supported by grants from NIH.]