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我搜集的一些资料: 海豚识别回声 内容好像有一个是海豚回声定位的 5次 讲海豚如何分辨同类的叫声和水下的杂音。
海豚对水里的声音的识别。。排除噪音，识别自己的回音。。。 講海豚如何分辨同類的叫聲和水下的雜音 海豚识别回声 海豚回声定位 1. 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。
记得有一个阅读关于海豚的声纳的 About how dolphins distinguish their own sounds from the others in the ocean
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clicks
Paragraph 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 有海豚那道，不过题目有点怪。 海豚识别回声
题目有点难 海豚识别回声
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这篇有点难，一开始就出来把我吓死了，虽然本月JJ有看到过，但是花了很多时间还是模模糊糊的，所以记得的不多，我有搜寻过以往的旧JJ，虽然有找到类似的海豚文章，似乎跟这篇不同。 豚利用click和emission來航海，並且能夠區分船隻的噪音，海底其他動物的聲音，同伴的聲音。比如一種蝦，發出的聲音很像是海豚發出的，人類一般不能區別出。[此處有題，答案是海豚對各種聲音的辨別力比人類強。]第二段開始講述海豚具體的辨別聲音的過程，比較複雜，大概是收到聲音後再自己發出聲音，然後通過回音等等來分辨。此處講到海豚的emission是有規律的頻率變化。[有題，問 emission的性質。答案是頻率改變，但是有規律可循，可以預測。] Echolcation - the location of objects by their echos - 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 echolcate 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 e ar 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 th e 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. | 
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发表于 2006-6-21 00:24:00
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