小抹香鲸回声定位信号高指向性发声机理

The high-directivity vocalization mechanism of echolocation signal of the pygmy sperm whale(Kogia breviceps)

齿鲸回声定位信号具有高频高指向性特性,使其能够精确感知水中目标,是现代声纳模仿的对象。本文通过分析小抹香鲸Kogia breviceps头部的几何结构与组织特性,采用双曲正割折射率材料模拟声速连续变化的额隆,并利用双曲正割折射率材料的最外侧声线轨迹对额隆的轮廓进行建模。在频域与时域两种模式下,应用有限元方法对仿真模型的远场指向性展开了分析,结果表明,点源经过具有双曲正割梯度折射率的额隆后在开口处形成了平面波,即额隆起到了准直的作用。通过对远场声压值分区域相关性分析表明,额隆的准直作用是形成较窄主瓣的主要原因,气囊和头骨则主要起到抑制旁瓣的作用。

The echolocation signal of odontocetes has the characteristics of high-frequency and high directivity,which enables it to accurately sense underwater targets and is the object imitated by modern sonar.In this paper,by analyzing the geometric structure and tissue characteristics of the head of the pygmy sperm whale(Kogia breviceps),the hyperbolic secant refractive index material is used to simu‐late the melon with continuous changing sound velocity,and the contour of the melon is modeled by the outermost sound track of the hyperbolic secant refractive index material.In frequency domain and time domain,the far-field directivity of the simulation model is analyzed by finite element method.The results show that the plane wave is formed at the opening after the point source passes through the melon with hyperbolic secant gradient refractive index,that is,the melon has the function of collima‐tion.By analyzing the correlation of far-field sound pressure values in different regions,it is shown that the collimation of the melon is the main reason for the formation of the narrower main lobe while the air sacs and the skull mainly play the role of suppressing the side lobe.