Level A Level B Level C TOEFL Incorrect word TOEFL reading comprehension Synonym TOEFL

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

Đọc đoạn văn sau và trả lời các câu hỏi:

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





Grammar Easy Grammar Medium Grammar - Difficult
1->25 26->49 50->75 76->99 100->125 126->164
Ôn Tập Ngữ Pháp Phần 1 Ôn Tập Ngữ Pháp Phần 2