The Auditory Mechanics of the Outer Ear of the Bush Cricket: A Numerical Approach
The Auditory Mechanics of the Outer Ear of the Bush Cricket: A Numerical Approach
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DOI：
10.1016/j.bpj.2019.11.3394
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发表时间：
2020-01-21
影响因子：
3.4
通讯作者：
Montealegre-Z, Fernando
中科院分区：
文献类型：
--
作者：
Celiker, Emine;Jonsson, Thorin;Montealegre-Z, Fernando
丛林蟋蟀的鼓膜耳朵位于前腿。它们的耳朵很精致，因为它们有外耳、中耳和内耳组成部分。外耳包括源自呼吸气管的充气管，即声气管（AT），其将声音从中胸声气门传递到腿中的鼓膜的内侧。AT的一个关键特征是它能够降低声音传播的速度并改变鼓室（鼓膜）的声学驱动力，从而在左右两侧之间产生声压和时间差，从而帮助动物的定向听觉。实验证明，气管声音传输产生类似于15 dB的增益和255 ms（-1）的传播速度，比自由场传播减少约25%。然而，造成声压级和声速变化的机制仍然难以捉摸。在这项研究中，我们调查的机械过程背后的声压增益在AT的气管声学行为的数值模拟，使用有限元方法和真实的三维几何形状的气管的灌木蟋蟀Copiphora gorgonensis。考虑到热粘性声壳相互作用对声音传播的影响，我们分析了喇叭形域，气管壁的材料特性，以及热过程对AT中声压级变化的影响。通过得到的数值结果，可以看出，气管的几何形状是主要因素，有助于观察到的压力增益。
Bush crickets have tympanal ears located in the forelegs. Their ears are elaborate, as they have outer-, middle-, and inner-ear components. The outer ear comprises an air-filled tube derived from the respiratory trachea, the acoustic trachea (AT), which transfers sound from the mesothoracic acoustic spiracle to the internal side of the ear drums in the legs. A key feature of the AT is its capacity to reduce the velocity of sound propagation and alter the acoustic driving forces of the tympanum (the ear drum), producing differences in sound pressure and time between the left and right sides, therefore aiding the directional hearing of the animal. It has been demonstrated experimentally that the tracheal sound transmission generates a gain of similar to 15 dB and a propagation velocity of 255 ms(-1), an approximately 25% reduction from free-field propagation. However, the mechanism responsible for this change in sound pressure level and velocity remains elusive. In this study, we investigate the mechanical processes behind the sound pressure gain in the AT by numerically modeling the tracheal acoustic behavior using the finite-element method and real three-dimensional geometries of the tracheae of the bush cricket Copiphora gorgonensis. Taking into account the thermoviscous acoustic-shell interaction on the propagation of sound, we analyze the effects of the horn-shaped domain, material properties of the tracheal wall, and the thermal processes on the change in sound pressure level in the AT. Through the numerical results obtained, it is discerned that the tracheal geometry is the main factor contributing to the observed pressure gain.