3.海豚的声呐系统

　　本月原始

　　V1：(by justmo)還有一篇是講dolphin通過sound跟whistle的頻率和模式來區分自己的和大海中其他的背景噪音 有細節題是問dolphin如何分別自己同其他的聲音 最後一段有說到dolphin發出聲音后會稍作等待再發出下一次emission 此處有題問這是爲什麽 像是這篇考古

　　V2(by第二篇：海豚 寂静有了 我就放个段落大意 可以看看考古 很全面的 题目不难

　　PI：海豚生活的环境中碰到很多噪音……但是他们就会比人类抵抗能力强(有考点)

　　P2：介绍了海豚们是怎么辨别出自己发出的声音的 ，主要是通过不同的rates 和什么来着忘了…… 并且它们会等自己的echo传回来以后再发出下一个(有考点)

　　题目：主旨题 details和考古里的一样

　　这篇也不难

　　悦读菌考古版

　　版本1

　　讲海豚的声纳系统。大概内容是说海豚的声纳系统很强，可以怎么怎么样。结构不是很清晰，但是无所谓因为考的好像都是细节题。其中 一题提到海豚的声纳系统可以区分很多人耳无法辨别的声音。(只记得这道了，都很简单)

　　版本2

　　第一段：海豚利用click和emission来航海，并且能够区分1船只的噪音，2海底其他动物的声音，3同伴的声音。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。]

　　第二段：开始讲述海豚具体的辨别声音的过程，比较复杂，大概是收到声音后再自己发出声音，然后通过回音等等来分辨。此处讲到海豚的emission(发射)是有规律的频率变化。[有题，问 emission的性质。答案是频率改变，但是有规律可循，可以预测。]

　　版本3

　　一 篇是讲海豚的 说海底有很多声音, 但海豚的click 和 whistle的行为, 可以让海豚间彼此沟通, 沟通是透过用不同频率的click和whistle repeat产生pattern 而且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(有题) 不是很长50行吧 考了一题assumption 一题细节 另一题记不清了

　　海豚门喜欢用声波确定方位，而且不同的海豚声波的频率还不一样。

　　海豚们在确定方位时会发出两种声波，一是d，一是whistle .d是稳定频率的声波而w是频率变换的声波。海豚们会发出声波然后等待声波回弹，根据回弹时间确定距离.

　　说海豚怎样在浅海里区别自己的声音和别的噪声。通过频率，重复的模式，回音的间隔时间等

　　版本4

　　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.