Fig. 1.

Auditory brain stem response (ABR) thresholds in CBA/CaJ and DBA/2J mice at 3 ages. While CBA/CaJ mice have little threshold shift up to an age of 7 mo, DBA/2J mice show a hearing loss that starts at high frequencies and progresses to lower frequencies as the mice age. Thresholds >70 dB sound pressure level (SPL) are indicated as 70 dB SPL due to limitations of the speaker used to deliver the test sounds. The number of mice tested in each group is indicated in parentheses in the legend. P16 and P21, postnatal days 16 and 21, respectively; 7m and 2m, 7 and 2 mo of age, respectively.