Numerical modeling of acoustic propagation in Harbor porpoise’s (Phocoena phocoena) head

Abstract

Harbor porpoises (Phocoena phocoena) use narrow band echolocation signals for locating prey and spatial orientation. In this study, acoustic impedance values of tissues in the porpoise’s head were calculated from the Hounsfield Units (HU). A two-dimensional finite element model was set up base on the computed tomography (CT) scan data to simulate the acoustic propagation through animal’s head. The far field transmission beam pattern in the vertical plane and the waveforms of the receiving points around the forehead were compared with prior measurement results, the simulation results were qualitatively consistent with the measurement results. The role of the main structures in the head such as air sacs, melon and skull in the acoustic propagation was investigated. Additionally, the relative sound pressure level within the porpoise’s sonar field across the transitional near and far field was obtained to compare with the spherical spreading loss.