Evidence for double acoustic windows in the dolphin, Tursiops truncatus.
In a bottlenose dolphin positions of sound receiving areas on the head surface were determined by comparing the acoustic delays from different sound-source positions. For this investigation, auditory brainstem responses (ABRs) to short tone pips were recorded and their latencies were measured at different sound source positions. After correction for the latency dependence on response amplitude, the difference in ABR latencies was adopted as being the difference of the acoustic delays. These delay differences were used to calculate the position of the sound-receiving point. Measurements were conducted at sound frequencies from 16 to 128 kHz, in half-octave steps. At probe frequencies of 16 and 22.5 kHz, the receiving area was located 21.7-26 cm caudal of the melon tip, which is near the bulla and auditory meatus. At higher probe frequencies, from 32 to 128 kHz, the receiving area was located from 9.3 to 13.1 cm caudal of the melon tip, which corresponds to a proximal part of the lower jaw. Thus, at least two sound-receiving areas (acoustic windows) with different frequency sensitivity were identified.
Popov
Vladimir V
VV
Institute of Ecology and Evolution of the Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia.
Supin
Alexander Ya
AY
Klishin
Vladimir O
VO
Tarakanov
Mikhail B
MB
Pletenko
Mikhail G
MG
D000162:Acoustics; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D050681:Bottle-Nosed Dolphin; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*