Echo-delay resolution in sonar images of the big brown bat, Eptesicus fuscus
Echo-delay resolution in sonar images of the big brown bat, Eptesicus fuscus
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DOI：
10.1073/pnas.95.21.12647
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发表时间：
1998-10-13
影响因子：
11.1
通讯作者：
Moss, CF
中科院分区：
文献类型：
--
作者：
Simmons, JA;Ferragamo, MJ;Moss, CF
回声定位大型褐蝙蝠(Eptesicus Fuscus)发射超声调频(FM)生物声纳声音(频率20-100 KHz，S周期10-50亩)，从回声延迟感知目标距离。知道延迟分辨率的敏锐度对于了解蝙蝠如何处理回声是至关重要的，因为蝙蝠从多个反射的延迟分离中感知目标的形状和纹理，蝙蝠可以单独感知两个同时产生的电子产生的回波的延迟，相隔仅2亩S，从而分辨距离接近0.3 mm的反射点(两点阈值)，这种两点分辨率大约比蝙蝠声音中最短的周期小五倍。由于蝙蝠的广播是2,000-4,500亩S，回波本身相互重叠和干扰，为了融合成一个单一的声音，其频谱由它们的相互干扰形成，取决于时间间隔的大小，为了单独感知重叠回波的延迟，BAT必须恢复当两个回波相互干扰时传递到频谱中的非常微小的延迟间隔信息，从而从回声频谱中明确地重建目标的距离像。然而，蝙蝠的2亩S分辨率极限如此之短，以至于可用的光谱线索极其有限。仅就拦截飞行昆虫而言，延迟的分辨率似乎过于尖锐，这表明蝙蝠的生物声纳图像具有更高的质量，以适应更广泛的定位任务，生物声纳回波处理相应地比人们怀疑的更复杂。
Echolocating big brown bats (Eptesicus fuscus) broadcast ultrasonic frequency-modulated (FM) biosonar sounds (20-100 kHz frequencies; 10-50 mu s periods) and perceive target range from echo delay. Knowing the acuity for delay resolution is essential to understand how bats process echoes because they perceive target shape and texture from the delay separation of multiple reflections, Bats can separately perceive the delays of two concurrent electronically generated echoes arriving as little as 2 mu s apart, thus resolving reflecting points as close together as 0.3 mm in range (two-point threshold),This two-point resolution is roughly five times smaller than the shortest periods in the bat's sounds. Because the bat's broadcasts are 2,000-4,500 mu s long, the echoes themselves overlap and interfere with each other, to merge together into a single sound whose spectrum is shaped by their mutual interference depending on the size of the time separation, To separately perceive the delays of overlapping echoes, the bat has to recover information about their very small delay separation that was transferred into the spectrum when the two echoes interfered with each other, thus explicitly reconstructing the range profile of targets from the echo spectrum. However, the bat's 2-mu s resolution limit is so short that the available spectral cues are extremely limited. Resolution of delay seems overly sharp just for interception of flying insects, which suggests that the bat's biosonar images are of higher quality to suit a wider variety of orientation tasks, and that biosonar echo processing is correspondingly more sophisticated than has been suspected.