听力文摘：隧道与广播

隧道与广播

How come we can hear FM longer in a tunnel than AM?

为什么在隧道中调频广播比调幅广播的信号要好一点？

It's because FM stations transmit at higher frequencies. They generally go from eighty-eight to one-hundred-and-eight megahertz. That's over a hundred million cycles per second.

这是因为调频广播台的传播频率要频繁些。通常在88到108兆赫。即每秒转1亿圈。

As a result, a single radio wave from an FM station is only a few meters long, about the size of a car. An AM station is putting out radio waves that are hundreds of times as long!

因此，调频广播电台发出的一个电波的长度只有几米，大概是一辆车的大小。而调幅广播站发出的电波长达几百米。

Long wavelengths¹ tend to be absorbed or blocked as they try to enter the smaller tunnel. The higher-energy and shorter-wavelength waves from an FM station aren't absorbed or blocked as much. Instead, they tend to bounce around and get reflected off of surfaces, much like the inside of a tunnel.

在穿越隧道时，长的波长会被吞并阻碍。而来自调频广播高能量，波长又短的电波则不会被吞并或阻碍。相反的，它们会被隧道表面反射回来。

Of course, they only bounce so far. If the tunnel is long enough, even FM stations fade out until you come out the other end.

当然，它们只会在某个区域内反弹。如果隧道太长的话，即使是调频广播也会逐渐变弱直到驶出隧道。

1 wavelengths   

n.波长( wavelength的名词复数 )；具有相同的/不同的思路；合拍；不合拍

参考例句：

• I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话，因为我们俩完全不对路。 来自《简明英汉词典》
• Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句