Jen P H, Chen D M
Division of Biological Sciences, University of Missouri-Columbia 65211.
Hear Res. 1988 Jul 15;34(2):101-17. doi: 10.1016/0378-5955(88)90098-6.
The directionality of sound pressure transformation at the pinna of three species of bats was studied by measuring the sound pressure level of a tone (25 45 65 and 85 kHz) at the tympanic membrane as a function of azimuth and elevation of the sound source under free-field conditions. The tympanic sound pressure level varied with location of the sound source. The directionality of sound pressure transformation pattern of the pinna of each bat was studied by plotting isopressure contours. The area within each isopressure contour decreased with increasing tonal frequency. For each tonal frequency, the point of maximal sound pressure was always located in the frontal ipsilateral sound field. This point shifted medially with increasing tonal frequency along the horizontal plane in all species tested, but it shifted in a species-specific manner along the vertical plane. Removal or distortion of the pinna and tragus resulted in either uncircumscribed or irregular isopressure contours for all tonal frequencies tested. Acoustic pressure gain of the external ear reached 16-23 dB for frequencies at 15-18 kHz. The importance of the external ear to the directionality of the bat's echolocation system is discussed.
通过在自由场条件下，测量作为声源方位角和仰角函数的鼓膜处某一音调（25、45、65和85千赫）的声压级，研究了三种蝙蝠耳廓处声压转换的方向性。鼓膜声压级随声源位置而变化。通过绘制等压轮廓线，研究了每只蝙蝠耳廓声压转换模式的方向性。每个等压轮廓线内的面积随音调频率增加而减小。对于每个音调频率，最大声压点始终位于同侧前方声场。在所有测试物种中，该点沿水平面随音调频率增加而向内移动，但沿垂直平面则以物种特异性方式移动。去除或扭曲耳廓和耳屏会导致所有测试音调频率的等压轮廓线无边界或不规则。对于15 - 18千赫的频率，外耳的声压增益达到16 - 23分贝。讨论了外耳对蝙蝠回声定位系统方向性的重要性。
