Temporal integration of threshold and suprathreshold signals

Abstract

A loudness summation study from this laboratory, using signal durations from 10 to 500 msec, failed to demonstrate a definite critical duration (i.e., a straight-line fit to the data gave r's:⩾0.97). A more extensive investigation, involving a number of durations beyond 500 msec, was undertaken to examine the problem in more detail. Employing 12 signal durations (from 10 msec to 3 sec) and using a transformed up/down procedure to collect the data, temporal integration functions at 1000 Hz were determined on six normal-hearing listeners both at threshold and at three suprathreshold intensities: 30, 60, and 90 dB SL. For the suprathreshold conditions listeners balanced the loudness of each tone to that of a 1-sec reference tone. Group data showed (1) evidence of a critical duration of somewhere between 150 and 300 msec at all levels, although this value was highly dependent upon how the critical duration was determined, and (2) some tendency toward reduced steepness of the loudness summation function below the critical duration with increasing level. [Work supported by the Research and Education Committee, Oklahoma City, V.A. Hospital.]