NCE4-L07 Bats 蝙蝠PPT

In what way does echo-location in bats play an utilitarian role?

In what way does echo-location in bats play an utilitarian role?

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.

MAURICE BURTON Curiosities of animal life

New words and expressions生词和短语

bat

n. 蝙蝠

strictly

adv. 明确地

utilitarian

adj.实用的

appreciation

n. 理解

elapse

v. 障碍物

hull

n. 消逝

interval

n. 船体

receipt

n. 间隔

apparatus

n. 收到

shoal

n. 仪器

herring

n. 鱼群

cod

n. 鳕鱼

squeak

n. 尖叫声

参考译文:

动物发出的声音并不都起语言作用。我们只需举发现蝙蝠的回声定位这个不同寻常的例子,就能知道声音起着极其实用的作用。要透彻理解这句话的含义,我们应先回顾人类最近的几项发明。

大家都知道,如果有人在墙壁或半山腰附近发出喊声,他就会听到回声。固体障碍物越远,回声返回所用时间就越长。敲打船体所发出的声音会从海底反射回来,测出回声与原声间隔的时间就可算出该处海洋的深度。目前船舶上普遍应用的回声探测仪就是这样产生的。凡是固体都反射声音,反射的声音因物体体积和质地各异而有所区别。鱼群亦会反射声音。因此,从测定海底深度到测定鱼群的位置这一进展相对较易。根据经验和改进了的仪器,人们不仅能确定鱼群的位置,还可以根据鱼群回声的特点辨别鲱鱼、鳕鱼还是其他人们熟知的鱼种。

人们已发现,某些蝙蝠能发出尖叫并通过回声确定并躲开障碍物,或找到它们赖以为生的昆虫。蝙蝠这种回声定位常与雷达相比较,二者原理相似。

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