title: Interaction of emitted sonar pulses and simulated echoes in a false killer whale: an evoked-potential study.
abstract: Auditory evoked potentials (AEP) were recorded during echolocation in a false killer whale Pseudorca crassidens. An electronically synthesized and played-back (simulated) echo was triggered by an emitted biosonar pulse, and its intensity was proportional to that of the emitted click. The delay and transfer factor of the echo relative to the emitted click was controlled by the operator. The echo delay varied from 2 to 16 ms (by two-fold steps), and the transfer factor varied within ranges from -45 to -30 dB at the 2-ms delay to -60 to -45 dB at the 16-ms delay. Echo-related AEPs featured amplitude dependence both on echo delay at a constant transfer factor (the longer the delay, the higher amplitude) and on echo transfer factor at a constant delay (the higher transfer factor, the higher amplitude). Conjunctional variation of the echo transfer factor and delay kept the AEP amplitude constant when the delay to transfer factor trade was from -7.1 to -8.4 dB per delay doubling. The results confirm the hypothesis that partial forward masking of the echoes by the preceding emitted sonar pulses serves as a time-varying automatic gain control in the auditory system of echolocating odontocetes.
authors: Institute of Ecology and Evolution of the Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia. alex_supin@mail.ru
authors: Alexander Ya
authors: AY
authors: Supin
authors: Paul E
authors: PE
authors: Nachtigall
authors: Marlee
authors: M
authors: Breese
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D000818:Animals; D001306:Auditory Pathways / Q000502:physiology*; D004289:Dolphins / Q000502:physiology*; D004455:Echolocation; D005072:Evoked Potentials, Auditory; D005260:Female; D010470:Perceptual Masking; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers