Listeners were asked to detect interaural differences of time in trains of 4000-Hz clicks as the interclick interval (ICI) was varied from 10 to 1 ms and the number of clicks in a train (n) was varied from 1 to 32. Plots of log interaural threshold versus log n produce straight lines whose absolute slopes decrease toward 0.0 with decreasing ICI. These results are shown to fit a saturation model which argues that as the click rate increases, the evoked neural activity moves from a response that is tonic toward one which is more phasic. The need to postulate neural compression is based in part on the fact that the three most commonly cited models of the limitations imposed by high frequency--reduction in the depth of modulations due to narrow-band filtering within the auditory system, neural refractoriness, and nonindependence of successive samples of internal noise--do not predict a change in slope with rate.