07 · 蝙蝠
Bats
区分观点、依据、例子与限制，用自己的话准确重建论述。
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Not all sounds made by animals serve as language, and we have only to turn to that extraordinary discovery of echo-location in bats to see a case in which the voice plays a strictly utilitarian role.
To get a full appreciation of what this means we must turn first to some recent human inventions. Everyone knows that if he shouts in the vicinity of a wall or a mountainside, an echo will come back. The further off this solid obstruction, the longer time will elapse for the return of the echo. A sound made by tapping on the hull of a ship will be reflected from the sea bottom, and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated. So was born the echo-sounding apparatus, now in general use in ships. Every solid object will reflect a sound, varying according to the size and nature of the object. A shoal of fish will do this. So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish. With experience, and with improved apparatus, it is now possible not only to locate a shoal but to tell if it is herring, cod, or other well-known fish, by the pattern of its echo.
It has been found that certain bats emit squeaks and by receiving the echoes, they can locate and steer clear of obstacles—or locate flying insects on which they feed. This echo-location in bats is often compared with radar, the principle of which is similar.
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整篇课文
Not all sounds made by animals serve as language, and we have only to turn to that extraordinary discovery of echo-location in bats to see a case in which the voice plays a strictly utilitarian role.
To get a full appreciation of what this means we must turn first to some recent human inventions. Everyone knows that if he shouts in the vicinity of a wall or a mountainside, an echo will come back. The further off this solid obstruction, the longer time will elapse for the return of the echo. A sound made by tapping on the hull of a ship will be reflected from the sea bottom, and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated. So was born the echo-sounding apparatus, now in general use in ships. Every solid object will reflect a sound, varying according to the size and nature of the object. A shoal of fish will do this. So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish. With experience, and with improved apparatus, it is now possible not only to locate a shoal but to tell if it is herring, cod, or other well-known fish, by the pattern of its echo.
It has been found that certain bats emit squeaks and by receiving the echoes, they can locate and steer clear of obstacles—or locate flying insects on which they feed. This echo-location in bats is often compared with radar, the principle of which is similar.
动物发出的声音，并不全都具有语言的作用。只要看看蝙蝠回声定位这一非凡发现，就能找到一个例子：声音在这里发挥的是纯粹实用的作用。
要充分理解这一点，得先看看人类近来的一些发明。大家都知道，在墙壁或山坡附近大喊，会有回声传来。这个坚实的障碍物离得越远，回声返回所需的时间就越长。敲击船身发出的声音会从海底反射回来，测出敲击与接收到回声之间的时间差，就能算出该处的水深。船上如今广泛使用的回声测深仪，就是这样产生的。一切固体都能反射声音，而回声会随物体的大小和性质有所不同。鱼群也不例外。因此，从探测海底到探测鱼群，只需要再向前迈一小步。有了经验，再加上改进后的仪器，人们如今不仅能找到鱼群，还能根据回声的特征，判断那是鲱鱼、鳕鱼，还是其他常见的鱼。
人们发现，某些蝙蝠会发出尖细的叫声，再通过接收回声来确定障碍物的位置并避开它们，或者找到作为食物的飞虫。蝙蝠的这种回声定位常被拿来与雷达相比，两者的原理相似。
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