|Title||Frequency-modulated up-chirp stimuli enhance the auditory brainstem response of the killer whale (Orcinus orca)|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Houser, Dorian S., Mulsow Jason, Almunia Javier, and Finneran James J.|
|Journal||The Journal of the Acoustical Society of America|
|EndNote Rec Number||12685|
|Keywords||auditory evoked potentials,bioacoustics,zoology|
Previous studies suggested that frequency-modulated tonal stimuli where the frequency sweeps upward (up-chirps) may enhance auditory brainstem response (ABR) amplitudes in mammals. In this study, ABRs were measured in response to up-chirps in three killer whales (Orcinus orca) and compared to ABRs evoked by broadband clicks. Chirp durations ranged from 125 − 2000 μs. Chirp spectral content was either “uncompensated,” meaning the spectrum paralleled the transmitting response of the piezoelectric transducer, or “compensated,” where the spectral density level was flat (+/−4 dB) across the stimulus bandwidth (10 − 130 kHz). Compensated up-chirps consistently produced higher amplitude ABRs than uncompensated clicks with the same peak equivalent sound pressure level. ABR amplitude increased with up-chirp duration up to 1400 μs, although there was considerable variability between individuals. Results suggest that compensating stimuli for the response of transducers can have a dramatic effect on broadband ABRs, and that compensated up-chirps might be useful for testing whale species where large size makes far-field recording of ABRs at the skin surface difficult.