through the speakers. Professor Jesse Barber says they found the sounds caused migratory (迁徙的) birds to flee. The birds also failed to gain weight.

　　Recently, researchers played the sounds of machines that are used to remove natural gas from the ground.

　　Professor Barber says these experiments are designed to help researchers learn the effects of noise pollution on birds, insects, bats, plants and people."We are testing the idea that these things are coupled - as the soundscape gets louder, wildlife suffers. But that also feeds back on how much people get out of that experience, how much they value it, and thus how much they are willing to protect that same place."

　　The research team also studied a group of volunteers who watch birds for fun. Mitch Levenhagen is a graduate student in the research team. He measured how much the artificial noise reduces the ability of the birdwatchers to identify recorded birdsong.

　　He recorded eight kinds of birdsong in the noise condition and another eight in the quiet. He then repeated the experiment without the artificial noise. The birdwatchers were happy when the noise machine was shut off.

　　The birdwatchers said the artificial noise affected their ability to identify bird sounds more than they thought it would. Birdwatcher Jim Lyons said the experiment caused him to value quiet more.

　　The National Park Service is paying for some noise pollution research. The federal agency is also examining other ways to reduce noise. They include putting new surfaces on roads. And they are creating quiet areas with signs telling visitors to turn off their mobile phones.

　　语篇解读：本文是一篇科普说明文。文章介绍了研究者通过研究噪音对鸟类的影响，进而表明自然环境中安静的重要性。

　　5．What effects does noise pollution cause to the birds?

　　A．They can't be heard singing again.

　　B．They escaped and can't put on weight.

　　C．The number of them reduces quickly.

　　D．They are afraid and easy to fly without direction.

　　解析：选B　细节理解题。根据第二段中的"they found the sounds caused migratory (迁徙的) birds to flee. The birds also failed to gain weight"可知，噪音让迁徙的鸟儿们逃离并且使它们不能增重。故选B项。

　　6．Why did the research team study some volunteers who watch birds for fun?

　　A．To identify the differences among different birdsong.

　　B．To figure out the reason why birdwatchers love watching birds.

C．To make sure of the effects that noise pollution has on the birds.