第 3 页精品文档---下载后可任意编辑SAT 阅读中的文化词条 请看以下两个词条的介绍: 1,Sonar Sonar is a technique that uses sound propagation (usually underwater) to navigate, communicate or to detect other vessels
Sonar may be used as a means of acoustic location
The term sonar is also used for the equipment used to generate and receive the sound
The frequencies used in sonar systems vary from infrasonic to ultrasonic
声纳一种利用水下声音传播来导航,联络或侦查其他船只的技术
它可用于声音定位
这个术语还指产生和接收声波的设备
声纳所使用的频率从次声到超声不等
2,Dolphins Dolphins are marine mammals that are closely related to whales and porpoises
There are almost forty species of dolphin in seventeen genera
They vary in size from 1
2 meters and 40 kilograms, up to 9
5 m and 10 ton
They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly e