Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency (频率) mix so that the highest point of one wave happens at the same time with the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle(周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars.
Another good thing about the use of noise-killing systems is that it saves the need for a silencer, which not only reduces the weight of a car, but also makes the motor burn less oil and work better.
Some engineers believe that the noise-killing system will be used in most cars in l996. But the carmakers haven't decided if they will put it into production because it would add several hundred dollars to the cost of their cars.
1. Which of the following gives a general idea of how the noise-killing system works?
A.By producing pressure waves going in the opposite direction.
B.By mising high frequency sound waves with low frequency sound waves.
C.By making copies of the unwanted sound waves and letting them out a little later.
D.By mixing new sound waves with the noise and sending them out together.
2. Besides its main function (功能) the noise-killing system can______.
【2017高考英语三轮冲刺阅读强化训练27】相关文章:
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (95)
★ 贵州省贵阳市2014高考英语(新人教版)一轮阅读训练(22)附答案
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (31)
★ 【三维设计】2017届高考英语(江苏专用)二轮复习完形填空解题技法示范课件:3
★ 2017届高考英语(江苏专用)二轮复习高考单词5大记忆法课件:4.联想记忆法
★ 2014高考英语(新人教版)一轮基础训练(17)A、B卷(附答案或解析)
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (17)
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21