Project report of virtual experiments in Marine bioacoustics: model validation

Abstract

A series of finite element model simulations are compared against results from various real world marine bioacoustics experiments with the bottlenose dolphin. Three significant results are revealed. 1) Changes in relative position of fat bodies can adjust echolocation beam direction. This is the first evidence of this. 2) Beam direction is consistent despite several elements being present within the sound transmission system within the dolphin's forehead. This suggests that the skull is the primary structural element in the formation of the sound transmission beam, with other elements playing a major role in concentrating or focusing the outgoing beam. 3) There is evidence for focusing of the beam in stages. The model simulations illustrate the narrowing of the sound transmission beam with various level of refinement in structural complexity. It appears as if structures like the melon and air space individually affect the narrowing of the beam, with their combined contributions being significant. All of these results are aligned with, or similar to, results obtained from live animals performing in psychoacoustic experiments over the past fifty years.