title: Dolphin and sea lion auditory evoked potentials in response to single and multiple swept amplitude tones.
abstract: Measurement of the auditory steady-state response (ASSR) is increasingly used to assess marine mammal hearing. These tests normally entail measuring the ASSR to a sequence of sinusoidally amplitude modulated tones, so that the ASSR amplitude function can be defined and the auditory threshold estimated. In this study, an alternative method was employed, where the ASSR was elicited by an amplitude modulated stimulus whose sound pressure level was slowly varied, or "swept," over a range of levels believed to bracket the threshold. The ASSR amplitude function was obtained by analyzing the resulting grand average evoked potential using a short-time Fourier transform. The suitability of this technique for hearing assessment of bottlenose dolphins and California sea lions was evaluated by comparing ASSR amplitude functions and thresholds obtained with swept amplitude and discrete, constant amplitude stimuli. When factors such as the number of simultaneous tones, the number of averages, and the frequency analysis window length were taken into account, the performance and time required for the swept-amplitude and discrete stimulus techniques were similar. The decision to use one technique over another depends on the relative importance of obtaining suprathreshold information versus the lowest possible thresholds.
authors: U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center, San Diego, CA 92152, USA. james.finneran@navy.mil
authors: James J
authors: JJ
authors: Finneran
authors: Jason
authors: J
authors: Mulsow
authors: Carolyn E
authors: CE
authors: Schlundt
authors: Dorian S
authors: DS
authors: Houser
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001299:Audiometry; D001306:Auditory Pathways / Q000502:physiology*; D001309:Auditory Threshold; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D005240:Feasibility Studies; D005260:Female; D005583:Fourier Analysis; D008297:Male; D011930:Reaction Time; D046070:Sea Lions / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013997:Time Factors