摘要：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 ge
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.
声纳一种运用水下声响传达来导航，联络或侦办其他船舶的技能。它可用于声响定位。这个术语还指发生和接纳声波的设备。声纳所运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 eating fish and squid. Dolphins are considered to be amongst the most intelligent of animals and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
海豚一种与鲸和钝吻海豚很挨近的海洋哺乳动物，包含17属近40种。海豚体型区别大，从身长1.2米体重40千克到身长9.5米体重10吨不等。海豚遍及世界各地，首要在浅海大陆架活动。属食肉动物，首要食物是鱼类和鱿鱼。海豚被认为是自然界智商最高的动物之一。因其友善的外表和形似生动的天分，被看作人类的老友。
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