Henze D, O'Neill W E
Department of Physiology, University of Rochester School of Medicine & Dentistry, New York 14642.
J Acoust Soc Am. 1991 May;89(5):2430-4. doi: 10.1121/1.400975.
The radiation patterns of the first three harmonics (approx. 30, 60, 90 kHz) of the mustached bat biosonar signal were measured from vocalizations elicited by cortical microstimulation. The primary foci of the acoustic beam patterns were in front of the mouth but somewhat below the horizontal plane. The prominent second and third harmonics showed sharp cutoffs between 20 degrees and 30 degrees lateral to the midline. Sidelobes were found, suggesting the influence of some vocal tract interference. When compared with previously measured estimates of the directionality of the auditory system, the vocal emission patterns are roughly complementary: Regions of maximum auditory sensitivity are found in areas of submaximal power for the sonar pulse beam pattern. The result is that, for the two most important harmonics, the "biosonar system" (i.e., vocal beam pattern plus receiver directionality) has a broader and more uniform directionality than either component alone. Therefore, within a limited region of space, echo amplitude will vary less as a function of angular displacement. This reduces the confounding influences of absolute sound pressure level on interaural intensity differences.
通过皮层微刺激引发的发声，测量了髭蝠生物声纳信号前三个谐波（约30、60、90千赫兹）的辐射模式。声束模式的主要焦点在嘴前方，但略低于水平面。突出的第二和第三谐波在中线外侧20度至30度之间显示出急剧截止。发现了旁瓣，表明存在一些声道干扰的影响。与先前测量的听觉系统方向性估计值相比，发声发射模式大致互补：在声纳脉冲束模式功率次最大的区域发现了最大听觉灵敏度区域。结果是，对于两个最重要的谐波，“生物声纳系统”（即声束模式加上接收器方向性）比单独的任何一个组件具有更宽且更均匀的方向性。因此，在有限的空间区域内，回波幅度随角位移的变化将更小。这减少了绝对声压级对双耳强度差异的混淆影响。
