Temporal summation and decay in hearing

Abstract

Two theories of temporal summation in hearing were compared. In both theories the ear performed a running average on the incoming sound in accordance with the convolution integral. In the rectangular theory sound was transformed by a power function and weighted by a brief rectangular function; in the exponential theory sound was transformed so that an initial large effect decays to a steady level and was weighted by a decaying exponential function. The rectangular theory predicted that brief tone bursts and brief gaps in a tone were equally detectable if the duration of the burst and gap were equal, but the exponential theory predicted that brief tone bursts were more readily detectable than brief gaps of equal duration. Experimental findings supported the exponential theory. The percentage of correct responses in a 2-alternative forced-choice task [in man] was greater for tone bursts than for tone gaps of equal duration. This result was obtained for tones and gaps from 25-200 ms in duration and for 2 different levels of a 1000-Hz tone. The exponential theory, with a time constant of 5 s-1 for the weighting function, was compatible with the relation between the percentage of correct responses and the theoretical quantity determining detectability.