新概念英語第四冊(含lrc文本)Lesson 7 Bats
- 聽力原文
- 參考譯文
Lesson 7
Bats
蝙蝠
First listen and then answer the following question.
聽錄音，然后回答以下問題。
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生詞和短語
bat
n. 蝙蝠
strictly
adv. 明確地
utilitarian
adj.實用的
appreciation
n. 理解
elapse
v. 障礙物
hull
n. 消逝
interval
n. 船體
receipt
n. 間隔
apparatus
n. 收到
shoal
n. 儀器
herring
n. 魚群
cod
n. 鱈魚
squeak
n. 尖叫聲
動物發(fā)出的聲音不都是用作語言交際。我們只要看一看蝙蝠回聲定位這一極不尋常的發(fā)現，就可以探究一下聲音在什么情況下有絕對的實用價值。 要透徹理解這句話的意義，我們應先回顧一下人類最近的幾項發(fā)明。大家都知道，在墻壁或山腰附近發(fā)出的喊聲，就會聽到回聲。固體障礙物越遠?；芈暦祷厮脮r間就越長。敲打船體所發(fā)了的聲音會從海底傳回來，測出回聲間隔的時間，便可算出該處海洋的深度。這樣就產生了目前各種船舶上普遍應用的回聲探測儀。任何固體者反射聲音，反射的聲音因物體的大小和性質的不同而不同。魚群也反射聲音。從測定海深到測定魚群，這一進展比較容易。根據經驗和改進了的儀器，不僅能夠確定魚群的位置，而且可以根據魚群回聲的特點分辨出是鯡魚、鱈魚，這是人們所熟悉的其他魚。 人們發(fā)現，某些蝙蝠能發(fā)出尖叫聲，并能通過回聲來確定并躲開障礙物，或找到它們賴以為生的昆蟲。蝙蝠這種回聲定位常?？膳c雷達相比較，其原理是相似的。
