Paragraph 1: 海豚怎样辨别自己的声音让专家觉得很有意思之类。。。因为在海里有很多很多的杂音。还举了一个浅水地方的例子，说海底里有很多小虾子发出的 clicksParagraph 2: 海豚发出的click trains and whistles seem designed to distinguish their own sounds from the others'. 而且whistles 有很规律性的变法 (unvarying pattern)。实验里面证明了海豚会等到接受了第一个clicks 的echo之后才发出第二个click trains 讲海豚如何分辨同类的叫声和水下的杂音 题目： Q1：海豚的声纳系统可以区分很多人耳无法辨别的声音：比如一种虾，发出的声音很像是海豚发出的，人类一般不能区别出。[此处有题，答案是海豚对各种声音的辨别力比人类强 Q2：问emission的性质，答案是频率改变，但是有规律可循，可以预测。] Q3：它们通常会在发出声音之后, 等一下听回音之类的, 藉以分辨出她们自己的声音和海底其它吵杂的声音 Q4：考了一题assumption 版本5
Echolocation - the location of objects by their echoes - is a highly specialized faculty that enables dolphins to explore their environment and search out their prey in a watery world where sight is often of little use. As sound travels four and a half times faster in water than in air, the dolphin's brain must be extremely well adapted in order to make a rapid analysis of the complicated information provided by the echoes. Although the ability to echolocate has only been proven experimentally for a few odontocete species, the anatomical evidence - the presence of the melon, nasal sacs and specialized skull structures - suggests that all dolphins have this ability. The dolphin is able to generate sound in the form of clicks, within its nasal sacs, situated behind the melon. The frequency of this click is higher than that of the sounds used for communication and differs between species. The melon acts as a lens which focuses the sound into a narrow beam that is projected in front of the animal. When the sound strikes an object, some of the energy of the soundwave is reflected back towards the dolphin. It would appear that the panbone in the dolphin's lower jaw receives the echo, and the fatty tissue behind it transmits the sound to the middle ear and thence to the brain. It has recently been suggested that the teeth of the dolphin, and the mandibular nerve that runs through the jawbone may transmit additional information to the dolphin's brain. As soon as an echo is received, the dolphin generates another click. The time lapse between click and echo enables the dolphin to evaluate the distance between it and the object; the varying strength of the signal as it is received on the two sides of the dolphin's head enable it to evaluate direction. By continuously emitting clicks and receiving echoes in this way, the dolphin can track objects and home in on them. The echolocation system of the dolphin is extremely sensitive and complex. Using only its acoustic senses, a bottlenose dolphin can discriminate between practically identical objects which differ by ten per cent or less in volume or surface area. It can do this in a noisy environment, can whistle and echolocate at the same time, and echolocate on near and distant targets simultaneously - feats which leave human sonar experts gasping.作者: 199249712 时间: 2012-4-16 14:35
支持一下 求确认。。就差这一篇了吧作者: 愁容骑士 时间: 2012-4-16 14:44
UP作者: lnl555 时间: 2012-4-16 16:27
顶了作者: lxd19870226 时间: 2012-4-16 16:50
谢谢分享