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 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 out the crests and troughs of noise. It then produces an electric current that is amplified and fed to a loudspeaker, which produces antisound 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- 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 and fog signals.

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

Câu hỏi liên quan

• The passage would most likely be followed by details about _______.

• The word “it” in paragraph 1 refers to________.

• How did the publication of Moby Dick affect Melville’s popularity?

ZUNIA12

• The word “informally” in this context mostly refers to an education occurring ...................

• How did the publication of Moby Dick affect Melville’s popularity?

• The word "their" in paragraph 1 refers to ______.

• Which of the following is the main topic of the passage?

• Which of the following is NOT true, according to the passage?

• In order to operate a computer, a student does not have to be _______

• Nowadays, there are ............

• After which year did the town really begin developing?

• In compared with low-achieving students, successful students use ...........

• The word cherished in paragraph 1 is closest in meaning to _______________

• The phrase “reach to the horizon” in paragraph 4 is closest in meaning to ______.

• What does the passage mainly discuss?

• Which form other than oral speech would be the most commonly used among blind people?

• The word “rupture” in bold in paragraph 3 is closest in meaning to .............

• The beverages mentioned in the first paragraph aim to give consumers  .............

• According to paragraph 2, evidence from fossil suggests that ...............

• What is the main idea of this passage?