Target echo processing in the dolphin´s auditory system

The dolphin´s auditory time resolution and integration time constant are believed to be around 0.3 ms. As long as multiple highlights in a target echo fall within the 0.3-ms auditory integration window, they generate the echo spectral characteristics, which are used by dolphins for the target identification. On the other hand, theoretical time resolution of the dolphin´s clicks is around 0.015 ms. Combination of very short echolocation clicks with a wide hearing frequency range from around 10 to 130 kHz suggests that the actual time resolution can be as high as the theoretical time resolution of the dolphin´s echolocation clicks. However, it always seemed doubtful that the theoretical time resolution of the dolphin´s clicks could be materialized in the relatively slow auditory system. The echolocation clicks are usually associated with the auditory target echo analysis in the frequency domain. Many results of our behavioral experiments with dolphins do indicate the dolphin´s auditory time resolution as high as 0.02-0.03 ms. This suggest that dolphins process target echoes with multiple highlights in the time domain. In this paper, some of our experimental results on temporal masking, temporal summation and double click discrimination in the bottlenose dolphin are presented.