『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 7 Lec 2听力练习：According to the professor, why does a pine tree produce a "smooth" echo?原文题目答案解析，TPO/Official 7 Lec 2听力原文范文音频翻译。

托福TPO/Official 7 Lec 2听力原文According to the professor, why does a pine tree produce a "smooth" echo?-新东方托福官方网校手机版

Narrator: Listen to part of a lecture in a Biology class.

教授：好了，大象就是这样来运用次声波的。

Prof: So, that is how elephants use infrasound.

现在我们来讲讲另一种声谱，一种极高的乃至人类听不见的声音：超声波。

Now, let‘s talk about the other end of the acoustical spectrum, sound that is too high for humans to hear：ultrasound.

超声波是许多动物用来侦查或识别的一种高频声音。

Ultrasound is used by many animals that detect and some of them send out very high frequency sounds.

卡罗：呃，蝙蝠。因为蝙蝠都没有视觉，所以它们不得不用声音来辨别方向，你知道的，以免飞行的时候撞到东西。

Carol: Well, bats, since they are all blind, bats have to use sound for, you know, to keep from flying into things.

回声定位其实就不言自明了，就是用回声反射声波来定位事物。

Echolocation is pretty self-explanatory; using echoes reflect to sound waves to locate things.

正像卡罗说的，蝙蝠用他们来导航和定位。

As Carol said, bats use it for navigation and orientation.

麦克：呃，觅食是一个重要的作用，而不会成为其他动物的食物也是一个功能。

Mike: Well, finding food is always important, and I guess not becoming food for other animals.

躲避捕猎者，定位猎物，昆虫基本都在夜间飞行。

Avoiding other predators, and locating prey, typically insects that fly around at night.

在我继续往下讲之前，我先回复一下刚刚卡罗说的问题，就是说蝙蝠都是没有视觉的。

Now before I go on, let me just respond to something Carol was saying: this idea that bats are blind.

其实，蝙蝠的一些物种是不依赖回声定位，而是用视觉进行导航的。但是确实，很多蝙蝠的视力太差了，基本起不到什么作用。

Actually, there are some species of bats, the ones that don't use echolocation that do rely on their vision for navigation, but it is true that for many bats, their vision is too weak to count on.

好了，我们迅速说一下回声定位适用的情况。

Ok, so quick summary of how echolocation works.

蝙蝠发出超声波脉冲，很高分贝的声波以至于我们听不到。

The bat emits these ultrasonic pulses, very high pitch sound waves that we can't hear.

然后，它们分析回声，声波是如何反射回来的。

And then, they analyze the echoes, how the waves bounce back.

在这里，让我先把课前提到的图表讲完。

Here, let me finish this diagram I started before class.

那么蝙蝠发出脉冲，就是很集中的一阵声音，然后回声反射。

So the bat sends out these pulses, very focused bursts of sound, and echoes bounce back.

You know, I don't think I need to draw on the echoes.

这是你们下周的阅读作业，其中会清晰的展示这个理论。

Your reading assignment for the next class, it has a diagram that shows this very clearly.

无论如何，正如我刚才说的，通过分析回声，蝙蝠就能知道，比如说，如果洞中有墙需要躲避，以及墙的距离有多远。

So, anyway, as I were saying, by analyzing these echoes, the bat can determine, say, if there is wall in a cave that it needs to avoid, and how far away it is.

超声波还有一个用途就是探测物体的大小和形状。

Another thing it uses ultrasound to detect is the size and shape of objects.

比如，它们迅速鉴别的一种回声方式和飞蛾有关，飞蛾是蝙蝠的一种食物，尤其是那种飞行时翅膀相交的飞蛾。

For example, one echo they quickly identify is the one they associate with a moth, which is common prey for a bat, particularly a moth beating its wings.

然而，飞蛾碰巧也比其他昆虫占有优势。

However, moth happened to have a major advantage over most other insects.

它们能够探察到超声波，这就意味着当蝙蝠靠近的时候，它们会知道蝙蝠的存在。

They can detect ultrasound, this means that when a bat approaches, the moth can detect the bat's presence.

因为，它们有时间逃到安全地带，或者它们也可以纹丝不动。

So, it has time to escape to safety, or else they can just remain motionless.

因为一旦它们不再煽动翅膀，蝙蝠就很难将它们从树叶或者其它物体辨别开来。

Since, when they stop beating their wings, they'd be much harder for the bat to distinguish from, oh...a leaf or some other object.

那么现在我们就知道动物在运用超声波的时候的非凡经验了。

Now, we have tended to underestimate just how sophisticated the abilities of animals that use ultrasound are.

事实上，我们推断蝙蝠在分析回声时过滤掉了很多因素。我们系统里精密的雷达能够忽略地面上静止物体的回声。

In fact, we kind of assumed that they were filtering a lot out, the way a sophisticated radar system can ignore echoes from stationary objects on the ground.

雷达借此可以剔除地面杂乱回波及关于山丘、建筑物等不必要的信息。

Radar does this to remove ground clutter, information about hills or buildings that it doesn't need.

而蝙蝠，我们起初认为它们过滤掉了很多因素，仅仅是因为它们不能够分析到这些因素。

But bats, we thought they were filtering out this kind of information, because they simply couldn't analyze it.

最近有一次关于树木和特种蝙蝠的实验。

Recently there was this experiment with trees and a specific species of bats.

这种蝙蝠叫做——激光枪鼻蝙蝠。

A bat called: the lesser spear--nosed bat.

那么，树木对于蝙蝠来讲应该是很大，且声学挑战极高对吧？

Now, a tree should be a huge acoustical challenge for a bat, right?

我的意思是，树木的表面形状角度各不相同。

I mean it's got all kinds of surfaces with different shapes and angles.

因此，从树木上反射的回声将会是大量且嘈杂的，是的，不像从飞蛾上反射回来那样简单。

So, well, the echoes from a tree are going to a mass of chaotic acoustic reflections, right, not like the echo from a moth.

我们一直以为蝙蝠对树的概念仅仅是树木而已。

So, we thought for a long time that bats stop their evaluation at simply that is a tree.

而结果却是有些种类的蝙蝠不仅能感知到树木，还能仅通过树叶就会区分开松树、落叶树，比如说枫树或者橡树。

Yet, it turns out that bats or at least this particular species, cannot only tell that is a tree, but can also distinguish between, say, a pine tree, and a deciduous tree, like a maple or oak tree, just by their leaves.

And when I say, leaves, I mean pine needles too.

学生：呃，比如飞蛾，就是树叶的形状？

Stu: Well, like with the moth, could it be their shape?

教授：思路很对。实际上是所有树叶组成整体的一个回声。

Prof: You are on the right track: It is actually the echo of all the leaves as whole that matters.

现在大家想象一棵松针并不茂密的松树，

Now, think, a pine tree with all those little densely packed needles.

那么就会产生许多简单的反射，我们称作：平滑回声。

Those produce a large number of faint reflections in what's... what's called a... a smooth echo.

这种声波非常的平均。但是橡树这种树叶少且树叶大的树木就会有更强的回声，会产生一种复杂的声波，或者我们称之为：粗糙回声。

The wave form is very even, but an oak which has fewer but bigger leaves with stronger reflections, produces a jagged wave form, or what we called: a rough echo.

而蝙蝠能够区别树木并不仅因为树木本身，而还是通过判断回声是平滑的还是粗糙的。

And these bats can distinguish between the two, and not just with trees, but with any echo that comes in a smooth or rough shape.

Why does the professor decide NOT to add more information to the diagram on the board?

According to the professor, what are two ways in which a moth might react when it detects the presence of a bat?

What surprising information did a recent experiment reveal about lesser spear-nosed bats?

According to the professor, why does a pine tree produce a "smooth" echo?

Narrator 
Listen to part of a lecture in a Biology class. 
Pro: So, that is how elephants use infrasound. Now, let’s talk about the other end of the acoustical spectrum, sound that is too high for humans to hear---ultrasound. 
Ultrasound is used by many animals that detect and some of them send out very high frequency sounds. So, what is a good example? Yes? Carol. 
Carol: Well, bats, since they are all blind, bats have to use sound for, you know, to keep from flying into things. 
Pro: That is echolocation. Echolocation is pretty self-explanatory; using echoes reflected sound waves to locate things. 
As Carol said, bats use it for navigation and orientation. And what else? Mike. 
Mike: Well, finding food is always important, and I guess not becoming food for other animals. 
Pro: Right, on both counts. Avoiding other predators, and locating prey, typically insects that fly around at night. Now before I go on, let me just respond to something Carol was saying--- this idea that bats are blind. Actually, there are some species of bats, the ones that don’t use echolocation that do rely on their vision for navigation, but it is true that for many bats, their vision is too weak to count on. 
Ok, so quick summary of how echolocation works. The bat emits these ultrasonic pulses, very high pitch sound waves that we cannot hear. And then, they analyze the echoes, how the waves bounce back. Here, let me finish this diagram I started before class. So the bat sends out these pulses, very focused bursts of sound, and echoes bounce back. You know, I don’t think I need to draw on the echoes, your reading assignment for the next class; it has a diagram that shows this very clearly. 
So, anyway, as I were saying, by analyzing these echoes, the bat can determine, say, if there is wall in a cave that it needs to avoid, and how far away it is. Another thing it uses ultrasound to detect is the size and shape of objects. For example, one echo they quickly identify is the one they associate with a moth, which is common prey for a bat, particularly a moth beating its wings. However, moth happened to have a major advantage over most other insects. They can detect ultrasound; this means that when a bat approaches, the moth can detect the bat’s presence. So, it has time to escape to safety, or else they can just remain motionless. Since, when they stop beating their wings, they’d be much harder for the bat to distinguish from, oh… a leaf or some other object. 
Now, we have tended to underestimate just how sophisticated the abilities of animals that use ultrasound are. In fact, we kind of assumed that they were filtering a lot out, the way a sophisticated radar system can ignore echoes from stationary objects on the ground. Radar does this to remove ground clutter, information about hills or buildings that it doesn’t need. 
But bats, we thought they were filtering out this kind of information, because they simply couldn’t analyze it. But, it looks as if we were wrong. Recently there was this experiment with trees and a specific species of bats. A bat called: the lesser spear nosed bat. 
Now, a tree should be a huge acoustical challenge for a bat, right? I mean it’s got all kinds of surfaces with different shapes and angles. So, well, the echoes from a tree are going to a mass of chaotic acoustic reflections, right, not like the echo from a moth. So, we thought for a long time that bats stop their evaluation at simply that is a tree. Yet, it turns out that bats or at least this particular species, cannot only tell that is a tree, but can also distinguish between, say, a pine tree, and a deciduous tree, like a maple or oak tree, just by their leaves. And when I say, leaves, I mean pine needles too. Any ideas on how it would know that? 
Stu: Well, like with the moth, could it be their shape? 
Pro: You are on the right track---it is actually the echo of all the leaves as whole that matters. Now, think, a pine tree with all those little densely packed needles. Those produce a large number of faint reflections in what’s... what’s called a ...a smooth echo. The wave form is very even, but an oak which has fewer but bigger leaves with stronger reflections, produces a jagged wave form, or what we called: a rough echo. And these bats can distinguish between the two, and not just with trees, but with any echo that comes in a smooth or rough shape. 
Now before I go on, let me just respond to something Carol was saying--- this idea that bats are blind. Actually, there are some species of bats, the ones that don’t use echolocation that do rely on their vision for navigation, but it is true that for many bats, their vision is too weak to count on. 
Ok, so quick summary of how echolocation works. The bat emits these ultrasonic pulses, very high pitch sound waves that we cannot hear.