nature20130103-4

来自丹麦南丹麦大学的科学家日前证实较小蝙蝠发射更高频率以实现定向声呐束,而可变的射束宽度对于蝙蝠至关重要,表明回声定位是一种允许不同种类蝙蝠(不考虑其身体大小)应答栖息地和任务时,聚集至最佳视野的动态系统。

-2013年1月3日《自然》


中文翻译


【题目】回声定位蝙蝠聚集声音视野

【译文】大多数回声定位蝙蝠身体大小与回声定位信号中最大能量的频率具有显著相关性,较小蝙蝠比较大蝙蝠利用更高的信号频率。通过所喜爱猎物的大小形成的尺寸信号异速增长或声波上增加的声波探测限制已被用于解释这一关系。本研究提出较小蝙蝠发射更高频率以实现定向声呐束,而可变的射束宽度对于蝙蝠至关重要的假说。与发射体大小相关的较短波长转换成更加定向的声呐束。因此,通过嘴发射信号的蝙蝠其嘴部大小和声波之间应表现出一种相关性,以驱动较小蝙蝠发射较高频率声波。我们发现在模拟近似栖息地的可飞行房间内,6只欧洲宽耳蝠(4-21g)产生相似形态和体积的声呐束。以10cm 20μPa均方根为参考,每种蝙蝠具有11±1 dB的指向性指数(37°的半振幅角度)以及108±4 dB声压级轴上声级。因此所有蝙蝠利用它们的声波信号实现声音视野。关键限制,这解释了蝙蝠大小与回声定位声波频率之间的关系。我们的结果表明回声定位是一种允许不同种类蝙蝠(不考虑其身体大小)应答栖息地和任务时,聚集至最佳视野的动态系统。

英文原稿


[Title]: Convergent acoustic field of view in echolocating bats

[Authors]:Lasse Jakobsen,1 John M. Ratcliffe1 & Annemarie Surlykke1

[Abstract]Most echolocating bats exhibit a strong correlation between body size and the frequency of maximum energy in their echolocation calls (peak frequency), with smaller species using signals of higher frequency than larger ones. Size–signal allometry or acoustic detection constraints imposed on wavelength by preferred prey size have been used to explain this relationship. Here we propose the hypothesis that smaller bats emit higher frequencies to achieve directional sonar beams, and that variable beam width is critical for bats. Shorter wavelengths relative to the size of the emitter translate into more directional sound beams. Therefore, bats that emit their calls through their mouths should show a relationship between mouth size and wavelength, driving smaller bats to signals of higher frequency. We found that in a flight room mimicking a closed habitat, six aerial hawking vespertilionid species (ranging in size from 4 to 21 g) produced sonar beams of extraordinarily similar shape and volume. Each species had a directivity index of 11±1dB (a half-amplitude angle of approximately 37°) and an on-axis sound level of 108 ± 4 dB sound pressure level referenced to 20 μPa root mean square at 10 cm. Thus all bats adapted their calls to achieve similar acoustic fields of view. We propose that the necessity for high directionality has been a key constraint on the evolution of echolocation, which explains the relationship between bat size and echolocation call frequency. Our results suggest that echolocation is a dynamic system that allows different species, regardless of their body size, to converge on optimal fields of view in response to habitat and task.

原文地址

http://www.nature.com/nature/journal/v493/n7430/full/nature11664.html

 

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