首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The idea of fighting a noise by making more noise sounds strange, but that’s exactly what motor engineers are doing in Germany a
The idea of fighting a noise by making more noise sounds strange, but that’s exactly what motor engineers are doing in Germany a
admin
2008-12-15
97
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.
Car makers’ research and development laboratories have already proved that mixing in more noise with the help of loudspeaker can reduce the unwanted noise.
Physicists have known about the technique for a long time. Sound is made up of pressure waves in tire air. If two sound waves of the same frequency mix so that the highest point of one wave happens at the same time as 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; this not only reduces the weight of a car, but also makes the motor burn less fuel and work better.
Some engineers believe that the noise-killing system will be used in most cars within a few years. 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.
选项
A、By producing pressure waves going in the opposite direction.
B、By mixing high frequency sound waves with low frequency sound waves.
C、By mixing new sound waves with the noise and sending them out together.
D、By making copies of the unwanted sound waves and letting them out a little later.
答案
C
解析
细节题。根据文章第三段“If two sound waves of the same frequency mix so that the highest point of one wave happens at the same time as 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.”所以[D]正确。
转载请注明原文地址:https://kaotiyun.com/show/yiNd777K
本试题收录于:
公共英语二级笔试题库公共英语(PETS)分类
0
公共英语二级笔试
公共英语(PETS)
相关试题推荐
Whatdidthemanwininhisdream?
Readthefollowingtextfromadiscussioninwhichfivewomentalkedabouttheirviewsonmarriage.Forquestions61to65,matc
Shoppingforclothesisnotthesameexperienceforamanasitisforawoman.Amangoesshoppingbecauseheneedssomething.
Drunkendriving—sometimescalledAmerica’ssociallyacceptedformofmurder—hasbecomeanationalepidemic.Everyhourofevery
Whatprobablyhappenedtotheman’sfather?
HelenSmith:WhatbetterwaytostartoffmysenioryearinhighschoolthanbyreadingsomethingIamentirelyfamiliarwit
Ifyouareworriedaboutthingsandareunderalotofstressatworkorschool,thenyouareprobablynotsleepingwell.Worry
JaneSmith:Well,IknowI’mgoodatmyjob,atleastmybosscallsmehard-working,conscientious,efficient.AsforwhenI
Asisknowntoall,theorganizationandmanagementofwagesandsalariesareverycomplex.Generallyspeaking,theAccountsDep
Howmuchdideachbottleofwhiskycost?
随机试题
为解决各类应用问题而编写的计算机程序称为_________。
Pickouttheappropriateexpressionsfromtheeightchoicesbelowandcompletethefollowingdialoguesbyblackeningthecorresp
在药典中收载了颗粒剂的质量检查项目,主要有
一般会计人员办理交接手续时的监交人员有()。
年末,单位本年度财政授权支付预算指标数大于零余额账户用款额度下达数的,根据未下达的用款额度,应该作出的分录为()。
下列法律事实中,属于法律事件的是( )。
离体的叶绿体在光照下进行稳定光合作用时,突然停止光照,短时间内,叶绿体内不可能发生的是()。
在分化、瓦解和改造犯罪分子中起重要作用的刑事政策是()。
利用游标机制可以实现对查询结果集的逐行操作。下列关于SQLServer2008中游标的说法中,错误的是()。
在E-R图中,图形包括矩形框、菱形框、椭圆框。其中表示实体联系的是______框。
最新回复
(
0
)