Physik Department T35, TU München, 85747 Garching bei Munchen, Germany.
J Acoust Soc Am. 2010 Aug;128(2):909-18. doi: 10.1121/1.3455853.
Lizards and many birds possess a specialized hearing mechanism: internally coupled ears where the tympanic membranes connect through a large mouth cavity so that the vibrations of the tympanic membranes influence each other. This coupling enhances the phase differences and creates amplitude differences in the tympanic membrane vibrations. Both cues show strong directionality. The work presented herein sets out the derivation of a three dimensional analytical model of internally coupled ears that allows for calculation of a complete vibration profile of the membranes. The analytical model additionally provides the opportunity to incorporate the effect of the asymmetrically attached columella, which leads to the activation of higher membrane vibration modes. Incorporating this effect, the analytical model can explain measurements taken from the tympanic membrane of a living lizard, for example, data demonstrating an asymmetrical spatial pattern of membrane vibration. As the analytical calculations show, the internally coupled ears increase the directional response, appearing in large directional internal amplitude differences (iAD) and in large internal time differences (iTD). Numerical simulations of the eigenfunctions in an exemplary, realistically reconstructed mouth cavity further estimate the effects of its complex geometry.
内部耦合耳，鼓膜通过一个大的口腔连接，从而使鼓膜的振动相互影响。这种耦合增强了相位差，并在鼓膜振动中产生幅度差。这两个线索都显示出很强的方向性。本文提出了一个内部耦合耳的三维解析模型的推导，该模型允许计算膜的完整振动轮廓。该解析模型还提供了结合非对称连接的听小骨的效果的机会，这导致了更高的膜振动模式的激活。通过包含此效果，解析模型可以解释取自活蜥蜴鼓膜的测量结果，例如，证明膜振动的非对称空间模式的数据。正如分析计算所示，内部耦合耳增加了定向响应，表现为大的定向内部幅度差（iAD）和大的内部时间差（iTD）。在一个典型的、真实重建的口腔中对本征函数的数值模拟进一步估计了其复杂几何形状的影响。
