首页
登录
职称英语
[originaltext] The idea of fighting a noise by making more noise sounds stra
[originaltext] The idea of fighting a noise by making more noise sounds stra
游客
2023-09-02
48
管理
问题
The idea of fighting a noise by making more noise sounds strange, but that’s exactly what motor engineers are doing in Germany and some other countries.
Carmakers’ research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise.
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 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, 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 by 1996. 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.
Questions 29 to 31 are based on the passage you have just heard.
29. Which gives a general idea of how the noise-killing system works?
30. What can the noise-killing system do besides its main function?
31. Why isn’t the noise-killing system yet popular?
选项
A、By producing pressure waves going in the opposite direction.
B、By mixing new sound waves with the noise and sending them out together.
C、By mixing high-frequency sound waves with low-frequency ones.
D、By making a copy of the unwanted sound waves and letting it out a little later.
答案
D
解析
选项均以“By+doing”开头表明,本题考查方式方法。短文中提到噪声消除系统的工作原理:如果两种相同频率的噪音混合,一种声波的最高点同时碰到另一种声波的最低点,噪音就消失了,接着提到对噪音进行完美复制,把复制的噪音推迟半个波周期,我们就可以消除不想要的噪音,D)的内容正是对此的同义转述,故答案为D)。
转载请注明原文地址:http://tihaiku.com/zcyy/2980188.html
相关试题推荐
[originaltext]Oneofthemaincomplaintsofcityresidents,notsurprisingl
[originaltext]Oneofthemaincomplaintsofcityresidents,notsurprisingl
[originaltext]WelcometotheCollegeLibraryservice.Wehaveawell-stock
[originaltext]W:Today’sgueston"ScienceUpdate"isDavidBrown.Dr.Brown,
[originaltext]W:Today’sgueston"ScienceUpdate"isDavidBrown.Dr.Brown,
[originaltext]W:Today’sgueston"ScienceUpdate"isDavidBrown.Dr.Brown,
[originaltext]W:NewYorkisafascinatingplaceandithasanotherinteresting
[originaltext]W:NewYorkisafascinatingplaceandithasanotherinteresting
[originaltext]W:NewYorkisafascinatingplaceandithasanotherinteresting
[originaltext]W:NewYorkisafascinatingplaceandithasanotherinteresting
随机试题
TheGibsonswerelittlegivento(i)________inanyform;notoneofthemwasaf
[originaltext]W:Itwasaheavystormlastnight,wasn’tit?M:Itcertainlywa
Itisimpossibleforparentsto________theirchildrenfromeverydanger.A、protec
按照公路工程造价组成,建设项目信息化费属于( )A.建设项目管理费 B.直接
在计算利息保障倍数时,其中的利息费用一般包括()。A.预收账款利息费用 B.
( )是衡量品德的重要标志。A.道德认识 B.道德意志 C.道德行为 D.
“己欲立而立人,己欲达而达人”告诉教师,对待同事和学生要做到( )。A.相互尊
抗生素属于()A.消毒剂 B.灭菌剂 C.抑菌剂 D.防腐剂 E.缓冲剂
男,54岁,2型糖尿病15年,长期口服格列本脲,10mg/d。查体:血压140/
依据《特种设备安全监察条例》的规定,锅炉、压力容器、电梯、起重机械、客运索道、大
最新回复
(
0
)