Temporal Summation of Acoustic Signals by the Chinchilla

The auditory sensitivity of two chinchillas was measured by means of a conditioned-avoidance technique. The signals were 2000-Hz sinusoids of 25, 50, 100, 200, 400, and 750 msec. The data were similar to the familiar temporal integration curve that has been reported for human subjects. Subsequently, the chinchillas were exposed for three hours to a 105-dB SPL octave-band of noise centered at 2000 Hz. The pre- and postexposure thresholds were measured for signals of 25, 200, and 750 msec. After exposure, the thresholds for all three stimuli were elevated, and they recovered to normal in approximately two weeks. The preexposure difference of 12 dB between the 25- and 750-msec signals was reduced after the noise exposure. During the process of recovery, the difference gradually returned to the preexposure magnitude.