【英语时差8,16】在回声中丢失的声音

Shout “HELLO” between two cliffs and you’ll hear the echoes as the sound waves bounce back and forth¹. But two things happen as the echoes bounce between the cliffs. First, the echoes get fainter because when the sound hits the cliff, not all of it comes back: some is absorbed by the rock, some bounces off in other directions, and some misses the cliff altogether.

    But your voice also gets distorted so that each succeeding echo sounds less like the original sound. Even though your voice contains a wide range of frequencies, what happens to those frequencies depends on the size, position, and material of the objects they come into contact with as they echo between the cliffs.

    Every situation is slightly different, but inevitably² some frequencies are more likely to be reflected while others simply fade away. So after a few echoes, the sound loses the characteristics of your voice and takes on new characteristics unique to the area you’re standing³ in. Real echoes usually fade away before they become that distorted, but you can see how it works with an artificial echo on two recorders. Say “hello” followed by your name into one recorder. Then play it back into the microphone of the other one. Play that recording⁴ back into the first recorder and so on back and forth about five to ten times.

    Gradually the two words will sound the same, as they lose their original characteristics and conform to the acoustic⁵ characteristics of the room and of the two recorders. Incidentally, this is a problem in concert halls, which have to be specially⁶ designed to reflect all the different frequencies accurately⁷.

1 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

2 inevitably   

adv.不可避免地；必然发生地

参考例句：

• In the way you go on,you are inevitably coming apart.照你们这样下去，毫无疑问是会散伙的。
• Technological changes will inevitably lead to unemployment.技术变革必然会导致失业。

3 standing   

n.持续，地位；adj.永久的，不动的，直立的，不流动的

参考例句：

• After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
• They're standing out against any change in the law.他们坚决反对对法律做任何修改。

4 recording   

n.录音，记录

参考例句：

• How long will the recording of the song take?录下这首歌得花多少时间？
• I want to play you a recording of the rehearsal.我想给你放一下彩排的录像。

5 acoustic   

adj.听觉的，声音的；(乐器)原声的

参考例句：

• The hall has a fine acoustic.这个大厅的传音效果很好。
• Animals use a whole rang of acoustic, visual,and chemical signals in their systems of communication.动物利用各种各样的听觉、视觉和化学信号来进行交流。

6 specially   

adv.特定地；特殊地；明确地

参考例句：

• They are specially packaged so that they stack easily.它们经过特别包装以便于堆放。
• The machine was designed specially for demolishing old buildings.这种机器是专为拆毁旧楼房而设计的。

7 accurately   

adv.准确地，精确地

参考例句：

• It is hard to hit the ball accurately.准确地击中球很难。
• Now scientists can forecast the weather accurately.现在科学家们能准确地预报天气。