蝙蝠
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Bats
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第1段
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.
动物发出的声音，并不全是用来传递信息的。只要看看蝙蝠回声定位这一非凡发现，就能知道声音也可以发挥纯粹的实用作用。
第2段
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.
要充分理解这意味着什么，我们必须回顾一下人类最近的一些发明。大家都知道，在墙壁或山腰附近大喊，就会听到回声。固体障碍物越远, 回声返回所用的时间就越久。敲打船身所发出的声音会由海底反弹回来，而利用接收回声的时间差，便可测算得出该处的海洋深度。这样就产生了目前各种船舶上普遍应用的回声探测仪。所有固体都会反射声音，因大小和性质而异。 鱼群也同样会反射声音。从定位海底到定位鱼群，仅一步之遥。 凭借着经验和升级了的仪器，人们不仅能够定位鱼群，还可以根据鱼群回声的模式分辨出是鲱鱼、鳕鱼，还是人们所熟悉的别的鱼。
第3段
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.
人们发现，某些蝙蝠能发出尖叫声，并能通过回声定位并躲开障碍物——或者定位它们作为食物的会飞的昆虫。蝙蝠的回声定位经常与雷达对比，两者的原理相似。
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译文与解析据吴应时整理资料及本站首轮审校稿；词伙与练习提示为本站学习设计。原PDF第33—35页，2022年2月第2版。