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  3. Complete silence is found only in laboratories called anechoic rooms. The walls and ceilings, made of blocks of special sound-su

Complete silence is found only in laboratories called anechoic rooms. The walls and ceilings, made of blocks of special sound-su

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问题     Complete silence is found only in laboratories called anechoic rooms. The walls and ceilings, made of blocks of special sound-sucking materials, are more than three feet thick, while floor coverings are six-foot layers of feathers or cotton wool. Silence here can be as painful to the ears as the din (continuous loud noise) of a steelworks or a rocket blast-off, yet scientists get used to this and stay in these silent rooms for hours at a time, using microphones and electronic equipment to test the various materials being developed to make the world a less noisy place.
    Architects have used scientific discoveries to solve noise problems in a number of ways. Walls are hollowed (having empty space inside) and then filled with sound-sucking materials similar to cotton wool. Extra-thick carpets cover the floors, and thick woolen curtains cover the windows. Air conditioning and heating channels are made less noisy by sound-sucking materials.
    Unfortunately, these techniques and others often work too well in some buildings. Noise-proof rooms become almost anechoic and people living in them are disturbed by the lack of sound. One way of handling this problem is to use what they call " sound perfume" — artificial ( similarly produced, made by man) noise is piped to rooms through small loudspeakers.
Scientists use anechoic room for______.
选项 A、measuring noise levels of steelworks
B、measuring blocks of feathers
C、testing sound-absorbing materials
D、testing electronic equipment
答案C
解析 科学家用消声室来______。细节题。从第一段最后一句话可以看出，科学家在消声室里测试各种各样的、可以降低噪音的材料。故答案为C。
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