評(píng)論
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Pro:So, that is how elephant uses infrasound.
教授:好了，大象就是這樣運(yùn)用次聲波的。
Now, let's talk about the other and the acoustic spectrums, sound that is too high for humans to hear-ultrasounds.
現(xiàn)在我們來(lái)講講另一種聲譜，一種極高的以致于人類聽(tīng)不見(jiàn)的聲音—超聲波。
Ultrasound is used by many animals that detected and some of them seen out very high frequency sounds.
超聲波是許多動(dòng)物用來(lái)偵查或識(shí)別的一種高頻聲音。
So, what is a good example? Yes, Kayo.
那么，能舉出什么好的例子嗎？嗯，卡陽(yáng)。
Kayo:Well, bats, since there is all blind, bats have to use sound for,
卡陽(yáng):我想到了蝙蝠。因?yàn)轵鸲紱](méi)有視覺(jué)，所以它們不得不用聲音來(lái)辨別方向，
you know, to keep them from flying in the things.
你知道的，以免飛行的時(shí)候撞到東西。
Pro:That is echolocation.
教授:那是回聲定位。
Echolocation is pretty self-explanatory; using echoes reflected sound waves to located things.
回聲定位其實(shí)不言自明，就是用回聲反射聲波來(lái)定位事物。
As Kayo said that bat used for navigation and orientation.
就像卡陽(yáng)舉出的導(dǎo)航和定位，
And what is else. Mike.
你還有什么例子呢？麥克。
Mike:Well, finding food is always important, and I guess not becoming food for other animals.
麥克:呃，覓食是很重要的，我猜是不想成為其他動(dòng)物的獵物。
Pro:Right, on both accounts.
教授:是的。兩個(gè)方面都對(duì)。
Avoiding other predators, and locating prey, typically insects that fly around it at night.
躲避捕獵者，定位獵物，昆蟲(chóng)基本都在夜間飛行。
Before I go on, let me just respond something Kayo was saying-this idea that is bats are blind.
在我繼續(xù)往下講之前，我先回復(fù)一下剛剛卡陽(yáng)說(shuō)的問(wèn)題，就是說(shuō)蝙蝠都是沒(méi)有視覺(jué)的。
Actually, there are some species of bats, the one that don't use echolocation that do rely on their vision for navigation,
其實(shí)，蝙蝠的一些物種是不依賴回聲定位，而是用視覺(jué)進(jìn)行導(dǎo)航的。
but its true for many bats, their vision is too weak to count on.
但是確實(shí)，很多蝙蝠的視力太差了，基本起不到什么作用。
Ok, so quick some rays if echolocation works.
好了，我們很快來(lái)講一下回聲定位適用的情況。
The bats emit the ultrasonic pulses, very high pitch sound waves that we cannot hear.
蝙蝠發(fā)出超聲波脈沖，很高分貝的聲波以致于我們?nèi)祟惵?tīng)不到。
And then, they analyze the echoes, how the waves bound back.
然后，它們分析回聲，聲波是如何反射回來(lái)的。
Here, let me finish the style diagram I started it before the class.
在這里，讓我先把課前提到的圖表講完。
So the bat sends out the pulses, very focus birds of sound, and echo bounds back.
那么蝙蝠發(fā)出脈沖，就是很集中的鳥(niǎo)聲，然后回聲反射。
You know, I don't think I need to draw the echoes, your reading assignment for the next class;
我想我不用畫聲波圖了，這將是我下節(jié)課給你們布置的閱讀作業(yè)，
it has diagram shows this very clearly.
其中會(huì)有圖表給你們很清晰的展示。
So,anyway, as I were saying, by analyzing this echo, the bat can determine,
無(wú)論如何，正如我剛才說(shuō)的，通過(guò)分析回聲，蝙蝠就能知道，
say, if there is wall in a cave that needs to avoid, and how far away it is.
比如說(shuō)，如果洞中有墻需要躲避，以及墻的距離有多遠(yuǎn)。
Another thing uses the ultrasound to detect is the size and the shape of objects.
超聲波還有一個(gè)用途就是探測(cè)物體的大小和形狀。
For example, one echo they quickly identified is one way associated with moff, which is common prey for a bat, particularly a moff meeting its wings.
比如，它們迅速鑒別的一種回聲方式和飛蛾有關(guān)，飛蛾是蝙蝠的一種食物，尤其是那種飛行時(shí)翅膀相交的飛蛾。
However, moff happened to have major advantage over most other insects.
然而，飛蛾碰巧也比其他昆蟲(chóng)占有優(yōu)勢(shì)。
They can detect ultrasound; this means that when the bat approaches, the moff can detect the bat's presence.
它們能夠探察到超聲波，這就意味著當(dāng)蝙蝠靠近的時(shí)候，它們會(huì)知道蝙蝠的存在。
So, it has time to escape to safety, or else they can just remain motionless. Since, when they stop meeting their wings, they will be much hard for the bat to distinguish from, oh… a leave or some other object.
因?yàn)椋鼈冇袝r(shí)間逃到安全地帶，或者它們也可以紋絲不動(dòng)。因?yàn)橐坏┧鼈儾辉偕縿?dòng)翅膀，蝙蝠就很難將它們從樹(shù)葉或者其它物體辨別開(kāi)來(lái)。
Now, we have tended to underestimate just how sophisticated the ability that animals that use ultrasound are.
那么現(xiàn)在我們就知道動(dòng)物在運(yùn)用超聲波的時(shí)候的非凡經(jīng)驗(yàn)了。
In fact, we kinds of assume that they were filtering a lot out.
事實(shí)上，我們推斷蝙蝠在分析回聲時(shí)過(guò)濾掉了很多因素。
The ways are sophisticated radar on our system can ignore the echo from the stationary object on the ground.
我們系統(tǒng)里精密的雷達(dá)能夠忽略地面上靜止物體的回聲。
Radar are does this to remove ground clutter, information about the hills or buildings that they doesn't need.
雷達(dá)借此可以剔除地面雜亂回波及關(guān)于山丘、建筑物等不必要的信息。
But bats, we thought they were filtering out kinds of information, because they simply couldn't analyze it.
而蝙蝠，我們起初認(rèn)為它們過(guò)濾掉了很多因素，僅僅是因?yàn)樗鼈儾荒軌蚍治龅竭@些因素。
But, it looks as we are wrong.
然而我們錯(cuò)了。
Recent there was the experiment with trees and specific species of bat.
最近有一次關(guān)于樹(shù)木和特種蝙蝠的實(shí)驗(yàn)。
A bat called:the laser spear nosed bat.
這種蝙蝠叫做激光槍鼻蝙蝠。
Now, a tree should be huge and acoustic challenge for bat, right?
那么，樹(shù)木對(duì)于蝙蝠來(lái)講應(yīng)該是很大，且聲學(xué)挑戰(zhàn)極高對(duì)吧？
I mean it got all kinds of surfaces with different shapes and angles.
我的意思是，樹(shù)木的表面形狀角度各不相同。
So, well, the echoes from trees are going to be massive and chaotic acoustic reflection, right, not like the echo from the moff.
因此，從樹(shù)木上反射的回聲將會(huì)是大量且嘈雜的，是的，不像從飛蛾上反射回來(lái)那樣簡(jiǎn)單。
So, we thought for a long time that the bat stop their evaluation as simply that is tree.
我們一直以為蝙蝠對(duì)樹(shù)的概念僅僅是樹(shù)木而已。
Yet, it turns out that is or at least particular species, cannot only tell that is trees, but can also distinguish between a pine tree, deciduous tree, like a maple or oak tree, just by their leaves.
而結(jié)果卻是有些種類的蝙蝠不僅能感知到樹(shù)木，還能僅通過(guò)樹(shù)葉就會(huì)區(qū)分開(kāi)松樹(shù)、落葉樹(shù)，比如說(shuō)楓樹(shù)或者橡樹(shù)。
And when I say, leaves, I mean pine needles too. Any idea on how we would know that?
我所謂的樹(shù)葉，還包括松針。知道我們?cè)趺传@悉的嗎？
Students:Well, like with the moff, could be their shape?
學(xué)生:呃，比如飛蛾，就是樹(shù)葉的形狀？
Pro:You are on the right track-it actually the echo of all the leaves as whole the matters.
教授:思路很對(duì)-實(shí)際上是所有樹(shù)葉組成整體的一個(gè)回聲。
Now, think, a pine trees with little densely packed needles.
現(xiàn)在大家想象一棵松針并不茂密的松樹(shù)，
Those produced a large number of fain reflection in which what's we called as:a smooth of echo.
那么就會(huì)產(chǎn)生許多簡(jiǎn)單的反射，我們稱作平滑回聲，
The wave forms were very even,
這種聲波非常的平均。
but an oak which has fewer but bigger leaves with stronger reflections, produces a gigots wave form, or what we called:a rough echo.
但是橡樹(shù)這種樹(shù)葉少且樹(shù)葉大的樹(shù)木就會(huì)有更強(qiáng)的回聲，會(huì)產(chǎn)生一種復(fù)雜的聲波，或者我們稱之為粗糙回聲。
And these bats can distinguish between a two, and not just was trees, but with any echo come in smooth and rough shape.
而蝙蝠能夠區(qū)別樹(shù)木并不僅因?yàn)闃?shù)木本身，而還是通過(guò)判斷回聲是平滑的還是粗糙的。
