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
To fight a noise by making more noise sounds strange, but that’ s exactly what motor engineers are doing in Germany and some oth
To fight a noise by making more noise sounds strange, but that’ s exactly what motor engineers are doing in Germany and some oth
admin
2012-10-16
91
问题
To fight a noise by making more noise sounds strange, but that’ s exactly what motor engineers are doing in Germany and some other countries.
Carmaker’ s research and development laboratories have already proved that mixing 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(频率) 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 (周期) ,we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise killing systems (系统)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 carry it into production because it would add several hundred dollars to the cost of their cars.
The noise killing system is not yet popular mainly because______.
选项
A、it is still being tried out
B、drivers still have their doubts
C、it increases the cost of car production
D、carmakers are not sure if it is necessary
答案
C
解析
推理判断题。从文章最后一段最后一句,But the carmakers haven’t decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.可知,因为费用太高,所以还未确定是否投入生产。
转载请注明原文地址:https://kaotiyun.com/show/MSwd777K
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
Thepassageimpliesthat______.WhichofthefollowingisTRUE?
Whatcanyouinferfromthetext?WhichofthefollowingisagoodtasteofdressinginAmerica?
【B1】【B20】
Whatistheprobablerelationshipbetweenthetwospeakers?
Whydidn’tthegirlgotothemovies?
--HowmuchwillIpayforthedinner?---twentydollarswill______allyouwanttohave.
______writingalettertothemanager,hedecidedtotalktohiminperson.
Howmanypeopledoesthestoryinvolve(涉及)?ThewritersaidthatChicagowasaverybigcity.Thatmeans______.
Marywas______byherneighbour’sruderemarks.
Chicagoisagreattown.Iloveit.Wehavetwobaseballteamshere,theCubsandtheWhiteSox.IliketheCubs.TheWhiteSox
随机试题
我国《收养法》规定,不满________周岁的未成年人可以被收养。()
重度子宫脱垂病人,手术后护理内容包括( )。
原方用法要求药后“多饮暖水”的是
患者男性,25岁,车祸大出血,需急诊手术,但无法取得患者意见又无家属或者关系人在场.医疗机构应如何处理
消化道分布有丰富的腺体,其中唾液腺主要包括
甲企业为增值税小规模纳税人,2016年11日购入一台生产用机器设备,取得普通发票60万元,税额为10.2万元,支付安装费,取得普通发票价款2万元,税O.22万元,计算甲该企业所得税计税基础的下列算式正确的是()。
组织策略是学习和记忆新信息的重要手段,下列活动中,学生运用组织策略的有()
材料(大意):2013年5月24日晚.网友“空游无依”发了一条微博,称他在埃及卢克索神庙的浮雕上看到有人用中文刻上了“丁锦昊到此一游”。“空游无依”表示.这是他在埃及感到最难过的一刻,简直无地自容。微博发出后,在社会上引起了轩然大波。至
由“十字军东征”这一事件评述东西方关系。
A、Onlyhumansrespondtoemotionsbysheddingtears.B、Onlyhumansshedtearstogetridofirritatingstuffintheireyes.C、On
最新回复
(
0
)