Temporal processing of paired clicks: monaural and binaural summation at threshold

Abstract

The threshold reduction that results from presenting the second of two equally intense clicks to either the same or the other ear after a brief interval (Δt) was measured using a three-interval forced-choice technique. The difference between thresholds for single clicks and click pairs randomized in the same session were measured monaurally for nine listeners and binaurally for 15 listeners. Summation of either monaural or binaural clicks was consistently less than would be predicted by a model of perfect energy summation, which concours with other studies using noise bursts of variable duration. The threshold reduction for a pair of monaural clicks was 2 dB at a Δt of 2 msec and even smaller reductions were obtained at longer Δt's. The threshold reduction for a pair of binaural clicks was 1.5 dB at interaural Δt's ranging from 0.01 to 15 msec. At Δt's ranging from 30 to 200 msec the threshold reductions for both binaural and monaural click pairs agreed with the level predicted by Green and Swets's “integration model” for the case of two independent observations.