A system for measuring distortion product otoacoustic emissions at ultra-sonic frequencies in rodents.

The aim of this work has been to construct and evaluate a system for recording distortion product otoacoustic emissions in rats at ultrasonic frequencies up to at least 50 kHz. The paper primarily describes the design of the acoustic probe system, as this is the most critical part. An acoustic ear simulator was developed and used for the subsequent calibration of the stimulus signals. A detachable probe system was provided in order to allow for visual inspection of the probe fitting in the ear canal prior to the final placement of the acoustic probe. Test/retest performance was evaluated by comparing DP-grams and I/O curves in 12 anaesthetized Wistar rats in two sessions separated approximately by one week. The between subject variance of the 12 tested rats appeared to be very modest, thus making the setup suitable for testing, for instance, ototoxicity of drugs or detection of cochlear damage due to noise exposures in rodents.