Lesson 7 Bats

Lesson 7 Bats 歌词

歌曲 Lesson 7 Bats
歌手 英语听力
专辑 新概念英语(第四册)
下载 Image LRC TXT
[00:01.47] Lesson 7
[00:03.39] Bats
[00:11.30] In what way does echo-location in bats play an utilitarian role?
[00:19.78]
[00:24.17] and we have only to turn to that extraordinary discovery of echo-location in bats
[00:30.34] to see a case in which the voice plays a strictly utilitarian role.
[00:36.35] To get a full appreciation of what this means
[00:39.73] we must turn first to some recent human inventions.
[00:44.50] Everyone knows that if he shouts in the vicinity of a wall or a mountainside,
[00:49.97] an echo will come back.
[00:52.57] The further off this solid obstruction,
[00:55.01] the longer time will elapse for the return of the echo.
[00:59.16]
[01:05.35] 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.
[01:15.11] So was born the echo-sounding apparatus, now in general use in ships.
[01:21.77] Every solid object will reflect a sound,
[01:25.65] varying according to the size and nature of the object.
[01:30.09] A shoal of fish will do this.
[01:32.95] So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish.
[01:40.85] With experience, and with improved apparatus,
[01:44.48] 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.
[01:56.28] It has been found that certain bats emit squeaks and by receiving the echoes,
[02:02.42] they can locate and steer clear of obstacles -- or locate flying insects on which they feed.
[02:09.96] This echo-location in bats is often compared with radar,
[02:14.16] the principle of which is similar.
[00:01.47] 第七节
[00:03.39] 蝙蝠
[00:11.30] 蝙蝠的回声定位在哪些方面有重大实用价值?
[00:19.78] 动物发出的声音不都是用作语言交际
[00:24.17] 我们只要看一看蝙蝠回声定位这一极不寻常的发现
[00:30.34] 就可以探究一下声音在什么情况下有绝对的实用价值
[00:36.35] 要透彻理解这句话的意义
[00:39.73] 我们应先回顾一下人类最近的几项发明
[00:44.50] 大家都知道,在墙壁或山腰附近发出的喊声
[00:49.97] 就会听到回声
[00:52.57] 固体障碍物越远
[00:55.01] 回声返回所用时间就越长
[00:59.16] 敲打船体所发出的声音会从海底传回来
[01:05.35] 测出回声间隔的时间,便可算出该处海洋的深度
[01:15.11] 这样就产生了目前各种船舶上普遍应用的回声探测仪
[01:21.77] 任何固体者反射声音
[01:25.65] 反射的声音因物体的大小和性质的不同而不同
[01:30.09] 鱼群也反射声音
[01:32.95] 从测定海深到测定鱼群,这一进展比较容易
[01:40.85] 根据经验和改进了的仪器
[01:44.48] 不仅能够确定鱼群的位置,而且可以根据鱼群回声的特点分辨出是鲱鱼、鳕鱼,这是人们所熟悉的其他鱼
[01:56.28] 人们发现,某些蝙蝠能发出尖叫声,并能通过回声
[02:02.42] 来确定并躲开障碍物,或找到它们赖以为生的昆虫
[02:09.96] 蝙蝠这种回声定位常常可与雷达相比较
[02:14.16] 其原理是相似的
Lesson 7 Bats 歌词
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