但裡面有一段話：「While some odontocetes are capable of echolocating swimbladderless prey, the majority of these cetaceans’ prey are free swimming, not buried……」顯示鯨豚能利用迴聲定位找出「自由游動」、「不具魚鰾」的獵物，所以應該不是被動收聽到沉浮的聲音。
加上另一段話：「Fishes without swimbladders have relatively weak acoustic signals, as
fish flesh has an acoustic impedance only 10% greater than water」顯然是因為缺少魚鰾的魚，身體的結構主要是肌肉，迴聲定位無法清楚地區分魚肉和水
#10
peregrine
2011/07/27
其實原文中已經記述：dolphins hunt partly by echolocating these bladders, which give off a strong acoustic signal。
But bottom-dwelling fish, such as barred sandperch don’t have swim bladders and so are harder to find with echolocation.
因而才會有本文討論為何海豚戴著海綿 。
聲納 是靠物體發出的聲音，來發現該物體。並無主動或被動的問題。
能迴聲定位無魚鰾的獵物是因為the majority of these cetaceans’ prey are free swimming, not buried….，也就是說，此些獵物是游動而不是潛藏著的，只要有動就有聲音，便能進行迴聲定位，容易與否取決於聲音的強弱。
原文中記述：dolphins hunt partly by echolocating these bladders, which give off a strong acoustic signal。海豚是藉由魚鰾(give off)發出的聲音，來進行迴聲定位。怎麼會是魚膘反彈回來的聲音？倘若是主動聲納判斷到魚膘反彈回來的聲音，才能準確定位。那麼為何只有魚膘反彈回來的聲音，才能準確定位，其他部位 不也一樣可以反彈聲音而被準確定位？
可能高中沒有談到海豚怎樣迴聲定位，也沒講到聲納有主動跟被動吧。
「Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them.」http://en.wikipedia.org/wiki/Animal_echolocation
所以「echolocating these bladders」的意思，在我解讀是：發出聲音，打到魚鰾，然後聽到迴聲」
言之有理，不過逆旅提供：「While some odontocetes are capable of echolocating swimbladderless prey, the majority of these cetaceans’ prey are free swimming, not buried……」，無魚鰾的獵物並無您所述情況，又如何被迴聲定位？
Echolocation is the same as active sonar, using sounds made by the animal itself. Ranging is done by measuring the time delay between the animal’s own sound emission and any echoes that return from the environment. 不是動物本身發出的聲音？該段取自http://en.wikipedia.org/wiki/A…
上段原文是記述的是，有的能迴聲定位無魚膘的獵物。所以才疑惑如何進行迴聲定位？Echolocation is the same as active sonar, using sounds made by the animal itself. Ranging is done by measuring the time delay between the animal’s own sound emission and any echoes that return from the environment. 這很清楚，不是動物本身必須發出聲音？
