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Reading comprehension -TOEFL- Lesson 97 (Đọc hiểu -TOEFL- Lesson 97)

Reading and answers the question:

   Sound moves form its source to the ear by wavelike fluctuations in
air pressure, something like the crests and troughs of ocean waves.
Once way to keep from hearing sound is to use ear plugs. Another
way is to cancel out the sound with anti-sound. Using a noisemarker
5 controlled by a microprocessor, engineers have produced sound waves
that are half a wavelength out of phase with those of the noise to
be quieted-each crest is matched to a trough, and vice versa. Once
the researchers have recorded the offending sound, a microprocessor
calculates the amplitude and wavelength of sound that will cancel
10 out the crests and troughs of noise. It then produces an electric
current that is amplified and fed to a loudspeaker, which produces
anti-sound and wipes out the noise. If the anti-sound goes out of
synchronization, a microphone picks up the leftover sound and sends
it back to the microprocessor, which changes the phase of the anti-
15 sound just enough to cause complete silence.

The research team has concentrated on eliminating low-frequency noise
from ship engines, which causes fatigue that can impair the efficiency
and alertness of the crew, and may mask the warning sounds of alarm
20 and fog signals.
1. What is the main purpose of the passage?

2. The passage compares sound to

3. The passage discusses a way to deal with an offensive noise by

4. One of the functions of the microprocessor described in the passage is to

5. The microprocessor described in the passage will probably be used for

6. The researcher mentioned in the passage are concerned about unwanted noise because it can

7. According to the passage, what group of people will probably first from the use of the microprocessor?

8. A paragraph following the passage would most probably discuss

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