Hearing is tested by auditory brain stem recordings (Tucker-Davis). Anesthetized mice are placed in a sound-attenuated chamber. Tone bursts (2 ms duration at 8, 16 and 32 kHz) and click stimuli (1 ms duration) are presented (21 per sec) via a free field electrostatic speaker. Responses are recorded over 10 ms. 1000 recordings are averaged. Click and tone burst stimuli are presented at intensities varying between 90 and 10 dB SPL in 10 dB intervals. Auditory thresholds are obtained by a visual comparison of wave forms.