Abstract:

Simultaneous tone masking and notch masking in conjunction with auditory-evoked potential recording was used to measure frequency tuning in dolphins. Tuning measurements within a range of 64--128 kHz using auditory brain-stem response (ABR) in conjunction with tone masking resulted in Q(10 dB) values of 16--18. However, this paradigm was unusable to measure frequency tuning at lower frequencies because ABRs are evoked by short transient acoustic stimuli of wide frequency band. To avoid this limitation, narrow-band sinusoidally amplitude-modulated tones were used as probes, which produce evoked potentials as an envelope-following response. With this method, tuning curves were obtained within the frequency range from 11.2--110 kHz. The Q(10 dB) values of the obtained curves varied from 12--14 at 11.2 kHz to 18--20 at 64--90 kHz. The data obtained with notch-noise maskers confirmed the results of tone masking: being approximated by roex filter form, they showed Q(10 dB) values of 18--20 and ERB of 35--39. Thus no tuning overestimation due to off-frequency listening occurred in the tone-masking experiments.