中华白海豚声接收通道

Sound reception pathway of the Indo-Pacific humpback dolphin

中华白海豚依靠其回声定位系统进行导航与目标探测.本文利用计算机断层扫描、超声测量与数值模拟研究中华白海豚声呐系统声接收过程.计算机断层扫描结果表明,中华白海豚声接收系统位于下颌区域.声接收通道主要包含下颌骨内侧脂肪、下颌骨外侧脂肪、下颌骨与听小骨.数值模拟结果表明,中华白海豚的声接收通道具有多样性.声波可沿着下颌骨传播至下颌内部脂肪,并随后传导至听小骨处.声波还可以通过下颌骨外侧脂肪进入声接收系统.声接收通道的多样性表明中华白海豚声呐系统的复杂性,探究声接收工作原理能加深下颌脂肪与下颌骨等多相介质形成的系统对声传播的控制,可为人工声接收系统设计提供新思路.

The Indo-Pacific humpback dolphins(Sousa chinensis)are nearshore odontocetes,distributed in tropical and sub-tropical oceans.This species has been studied to unveil its ability to echolocate.Indo-Pacific humpback dolphin,like its Odontocetes companion,relies on echolocation system to navigate and detect targets,which contains a sound transmitting system in the forehead and a sound reception in the jaw.Their soft tissues present gradient sound speed and density distributions in the forehead.Solid skull,air structures and soft tissues form a natural multi-phase meta-material to modulate sounds into energy focused beams.This multiphase property is also applied to the hearing system as revealed in current papers.Here in this work,the physical mechanism of sound reception in the Indo-Pacific humpback dolphin is studied by using the computed tomography(CT)scanning,physical measurements and numerical simulation.Hounsfield units(HUs)of the forehead tissues are extracted from CT scanning results.A linear relationship is revealed between HU and sound speed,HU and density,which are combined with HU distribution to reconstruct the sound speed and density distribution of the sound reception system.The CT scanning shows that the sound reception system located at lower head is composed of external mandibular fat,internal mandibular fat,mandible and hearing bones.Model of sound reception system is developed on the basis of CT scanning results and used in subsequent simulations.The physical process of sound reception reveals that the hearing system can guide sounds through variable pathways to reach hearing bones.Sounds can enter into the reception system along the acoustic pathways composed of mandible,external mandibular fat and internal mandibular fat.Mandibular fat and mandible form a unique sound pathway.In addition,another pathway which is composed of external mandibular fat,pan bone and internal mandibular fat can lead the sound to propagate and finally arrive at hearing bones.The diversity of acoustic pathways is applicable to a range of frequencies from 30 to 120 kHz.The variability of acoustic pathways in Indo-Pacific humpback dolphin shows the complexity of its biosonar system.The anatomy and simulation results can deepen our understanding of the mechanism of echolocation of Indo-Pacific humpback dolphin and provide references for designing man-made sound reception devices.