Simulate the Indo-Pacific humpback dolphin's beam formation through finite element method: based on the reconstruction of the dolphin's sound velocity distribution

The Indo-Pacific humpback dolphin (Sousa chinensis), is believed to use sophisticated bio-sonar for navigation, orientation and foraging. Acoustic properties of its head have not yet been studied and are essential to study the dolphin biosonar system. In this paper, sound velocity distribution of an Indo-Pacific humpback dolphin head was reconstructed based on ultrasound measurement and computed tomography (CT) imaging. The linear relation between sound velocity and Hounsfield unit was determined by regression analysis to derive sound velocity distribution in the dolphin head. Density distribution was derived by combining the sample head CT distribution with the linear relation between the Hounsfield unit and density acquired from previous experimentation. Based on these acoustic parameters, the beam formation process of the species was then researched through the finite element method. The results showed that, within the frequency range, the emitted sound's energy was highly focused, forming main beams in the forward direction.