The role of pressure difference reception in the directional hearing of budgerigars (Melopsittacus undulatus)
The role of pressure difference reception in the directional hearing of budgerigars (Melopsittacus undulatus)
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DOI：
10.1007/s00359-006-0138-1
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发表时间：
2006-10-01
影响因子：
2.1
通讯作者：
Michelsen, Axel
中科院分区：
文献类型：
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作者：
Larsen, Ole N.;Dooling, Robert J.;Michelsen, Axel
在许多鸟类中，中耳通过充满空气的耳间通道相连。通过这一途径的声音传输可以改善方向性听力。然而，试图证明这种机制产生了相互矛盾的结果。其中一个原因是，一些鸟类在麻醉时，中耳的静态气压较低，从而减少了耳膜的振动。在麻醉的虎皮鹦鹉中，我们发现通过耳间通道传播的声音大大改善了定向听力的线索。接收声音的方向性线索与声音在耳间通路传播的振幅增益和时间延迟相结合，定量地解释了耳膜振动对声音入射方向的依赖性。耳间声传播是鼓膜振动额部梯度的主要原因（即声源从对侧小角度移动到同侧小角度时）。我们的研究证实，在低频率的耳间声音传播可能导致鼓膜的振动在时间上有很大差异，从而为定向听力提供了可能的线索。我们的鸟类头部的声学有效尺寸（直径28毫米）比头骨的尺寸预期的要大得多，所以显然头上的羽毛有相当大的声学效果。
In many birds, the middle ears are connected through an air-filled interaural pathway. Sound transmission through this pathway may improve directional hearing. However, attempts to demonstrate such a mechanism have produced conflicting results. One reason is that some species of birds develop a lower static air pressure in the middle ears when anaesthetized, which reduces eardrum vibrations. In anaesthetized budgerigars with vented interaural air spaces and presumed normal eardrum vibrations, we find that sound propagating through the interaural pathway considerably improves cues to the directional hearing. The directional cues in the received sound combined with amplitude gain and time delay of sound propagating through the interaural pathway quantitatively account for the observed dependence of eardrum vibration on direction of sound incidence. Interaural sound propagation is responsible for most of the frontal gradient of eardrum vibration (i.e. when a sound source is moved from a small contralateral angle to the same ipsilateral angle). Our study confirms that at low frequencies the interaural sound propagation may cause vibrations of the eardrum to differ much in time, thus providing a possible cue for directional hearing. The acoustically effective size of the head of our birds (diameter 28 mm) is much larger than expected from the dimensions of the skull, so apparently the feathers on the head have a considerable acoustical effect.