Group averaged ABR waveforms, evoked by 65 dB SPL stimuli, are plotted for mutant mice (red lines) and heterozygous littermate controls (black lines) aged 2 weeks (A-C), 3 weeks (D-F) and 6 weeks (G-I) in response to click stimuli (A,D,G), 12 kHz stimuli (B,E,H) and 24 kHz stimuli (C,F,I). Group averaged ABR waveforms, evoked by stimuli presented at 20 dB above threshold (20 dB sensation level, dB SL), are plotted for mice aged 2 weeks (J-L), 3 weeks (M-O), 6 weeks (P-R) in response to click stimuli (J,M,P), 12 kHz stimuli (K,N,Q) and 24 kHz stimuli (L,O,R). Group sizes were, at 2 weeks old, n = 13 control mice, n = 12 mutants; at 3 weeks old, n = 8 control mice, n = 19 mutants; at 6 weeks old, n = 17 controls, n = 10 mutants.