首页
登录
职称英语
To fight a noise by making more noise sounds strange, but that’s exactly wha
To fight a noise by making more noise sounds strange, but that’s exactly wha
游客
2025-07-31
11
管理
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.
Car makers’ 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.
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 tire unwanted sound waves and letting them out a little later.
答案
D
解析
从文章第三段第四句Therefore,by producing a perfect copy of the noise and delaying it by half a wave cycle,we call kill the unwanted noise.得知。
转载请注明原文地址:https://tihaiku.com/zcyy/4184591.html
相关试题推荐
Tofightanoisebymakingmorenoisesoundsstrange,butthat’sexactlywha
【B1】[br]【B6】A、smileB、lookC、stareD、shoutA承接上句的smilingatstrangers,选A。
【B1】[br]【B13】A、producingB、speakingC、makingD、doingC显然与differenttechniques
Carefulandcarelessareasdifferentasfireandwater.Butstrangelyenou
【B1】[br]【B7】A、directB、familiarC、strangeD、funnyB文中指出,由于作者跟这里的所有人都很熟,所以他们在说话
He______themaking-upexamyesterday.A、tookB、joinedC、attendD、tookpartinA
【B1】[br]【B9】A、workmateB、comradeC、strangerD、friendCworkmate意为“工友,同事”;comra
【B1】[br]【B4】A、neighbourB、strangerC、nativeD、relativeBneighbour邻居;stranger陌生
Whatmustyoudofirstwhenmakingavalentinebox?[br][originaltext]Vale
Whatmustyoudofirstwhenmakingavalentinebox?[originaltext]Valentine
随机试题
TheHopeProjectaimstobringhopetopeoplestrugglingwithadisabilityan
Wecanacceptyourorderoncondition______(你们提前付款).thatyoupayinadvance本题考
营造医院环境的原则是()A.动态性与稳定性统一的原则 B.审美化与道德
某市一化工厂,占地面积为12.9ha,企业有员工140人,主要为周边村庄百姓。2
隧道全断面开挖可用于()。A.I~Ⅲ级围岩中小跨度隧道 B.I~Ⅲ级围岩
(材料)核心内容函数是中学数学的核心内容,以函数思想来贯穿中学数学内容更有利于
某企业“生产成本”账户的期初余额为10万元,本期为生产产品发生直接材料费用80万
表现在人对现实的态度和惯常的行为方式中比较稳定的心理特征是() A、道德感
某技术改造项目有3个互斥方案,假设收益率为10%。见下表: ()应被淘
下列交易或事项中,属于会计政策变更的有()。A.坏账准备计提方法由余额百分比法
最新回复
(
0
)