Fuzessery Z M
Department of Psychology, University of Wyoming, Laramie 82071, USA.
Hear Res. 1996 May;95(1-2):1-17. doi: 10.1016/0378-5955(95)00223-5.
The acoustic properties of external ears transform the spectra of incident sound in a location-dependent manner, and provide monaural and binaural spectral information used in 2-dimensional localization. Human studies suggest that binaural spectral differences, and spectral peaks and notches in monaural transfer functions, may all provide spatial information. This study examined the acoustic properties of the pallid bat ear to determine directionality, interaural intensity differences spectral peaks and notches in transfer functions, as well as acoustic gain. The pallid bat is a gleaning bat that uses passive sound localization to find prey, and echolocation for general orientation. It is capable of very accurate passive sound localization, and the primary focus of this study was to determine the spectral cues that might support this localization acuity. Results show that the external ears of this bat create spectral maxima and minima that vary systematically with azimuth and elevation. The monaural spectral cues resemble those reported in humans and cats and suggest that similar spectral cues are used across taxa. The ears also create robust interaural spectral differences that vary systematically with both sound azimuth and elevation. These monaural and binaural spectral cues may provide the basis for the 1 degrees angular resolution apparent in it this bat's passive sound localization performance.
外耳的声学特性以位置依赖的方式改变入射声音的频谱，并提供用于二维定位的单耳和双耳频谱信息。人体研究表明，双耳频谱差异以及单耳传递函数中的频谱峰值和谷值可能都提供空间信息。本研究考察了苍白洞蝠耳朵的声学特性，以确定其方向性、双耳强度差异、传递函数中的频谱峰值和谷值以及声学增益。苍白洞蝠是一种食虫蝙蝠，它利用被动声音定位来寻找猎物，并通过回声定位进行总体定向。它能够进行非常精确的被动声音定位，本研究的主要重点是确定可能支持这种定位敏锐度的频谱线索。结果表明，这种蝙蝠的外耳会产生随方位角和仰角系统变化的频谱最大值和最小值。单耳频谱线索与人类和猫中报道的相似，表明不同类群使用相似的频谱线索。耳朵还会产生强大的双耳频谱差异，这种差异会随着声音方位角和仰角而系统地变化。这些单耳和双耳频谱线索可能为这种蝙蝠被动声音定位表现中明显的1度角分辨率提供基础。
