This study examined the deleterious effects of a later-arriving sound on the processing of interaural differences of time (IDTs) from a preceding sound. A correlational analysis assessed the relative weight given to IDTs of source and echo clicks for echo delays of 1-64 ms when the echo click was attenuated relative to the source click (0-36 dB). Also measured were proportion correct and the proportion of responses predicted from the weights. The IDTs of source and echo clicks were selected independently from Gaussian distributions (μ=0 μs, σ=100 μs). Listeners were instructed to indicate the laterality of the source click. Equal weight was given to the source and echo clicks for echo delays of 64 ms with no echo attenuation. For echo delays of 16-64 ms, attenuating the echo had no substantial effect on source weight or proportion correct until the echo was attenuated by 18-30 dB. At echo delays ≤4 ms, source weights and proportions correct remained high regardless of echo attenuation. The proportions of responses predicted from the weights were lower at echo delays ≥16 ms. Results were discussed in terms of backward recognition masking and binaural sluggishness and compared to measurements of echo disturbance.
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We would like to thank our colleagues at the Parmly Hearing Institute for their support and advice while this experiment was conducted. We would also like to thank Dr. Wes Grantham, Dr. Gerald Kidd, and an anonymous reviewer for many helpful suggestions that improved the clarity of the manuscript. In particular, it was the anonymous reviewer who suggested that we consider room sizes for cases in which the source and the listener were in close proximity. José A. Gallegos was supported by the Mie Kim Najita Summer Fellowship. James Collier provided technical assistance and Noah Jurcin assisted with data collection. This work was supported by a grant from NIDCD (Program Project Grant No. DC000293). 1