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
Sound moves from its source to the ear by wave like fluctuations in air pressure, something like the peaks and troughs or the lo
Sound moves from its source to the ear by wave like fluctuations in air pressure, something like the peaks and troughs or the lo
admin
2013-01-25
47
问题
Sound moves from its source to the ear by wave like fluctuations in air pressure, something like the peaks and troughs or the lowest point of ocean waves. One way to keep from hearing sound is to use ear plugs. Another way is to cancel out the sound with anti-sound.
Using a noise maker controlled by a microprocessor, engineers have produced sound waves that are half a wavelength out of phase with those of the noise to be quieted--each peak is matched to a trough, and vice versa. Once the researchers have recorded the offending sound, a microprocessor calculates the amplitude and wavelength of sound that will cancel out the highest and lowest points of the noise. It then produces an electric current that is amplified and fed to a loudspeaker, which produces anti-sound and wipes out the noise. If the anti-sound goes out of synchronization, a microphone picks up the leftover sound and sends it back to the microprocessor, which changes the phase of the anti-sound just enough to cause complete silence.
The research team has concentrated on eliminating low-frequency noise from ship engines, which causes fatigue that can impair the efficiency and alertness of the crew, and may mask the warning sounds of alarm and fog signals.
The passage compares sound to ______.
选项
A、the rising and falling of water in the ocean
B、the crests and valleys of mountain ranges
C、a flag waving in the air
D、a machine for measuring air pressure
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/tF1O777K
0
考博英语
相关试题推荐
Thegovernmentistryingtodosomethingto____betterunderstandingbetweenthetwocountries.
Behaviorsthatwedonotunderstandoftenbecomenearlyinvisible-evenwhen,inretrospect,weseehowtrulystrangetheyare.
Onceapictureisprovedtobeaforgery,itbecomesquite_____.
Thegovernmentrecentlypresentedanambitiousplantotackletheviolenceand_____thatfollowwhentoomanypeopledrinktoomu
Researchersfindithardto________thetwosetsoffigures.
Thecomputercanbeprogrammedto________awholevarietyoftasks.
Wehadbeentakenoverbyanotherfirm,andamanagement_____wasunderway.
Ourspeciesevolvedonthemove.Recentresearchontheeffectsofexerciseandtheconsequencesofsedentarylivinghasshownt
Researcherswhorefusetosharedatawithothersmay【51】otherstowithholdresultsfromthem,【52】astudybyhealth-policyanalys
Researcherswhorefusetosharedatawithothersmay【51】otherstowithholdresultsfromthem,【52】astudybyhealth-policyanalys
随机试题
关于胃癌转移的描述,正确的是
根据有关招标投标规定,资格预审公告或招标公告应当在“三报一网”中的至少一个媒介发布,下列属于“三报一网”的是()。
软交换控制设备是软交换体系架构网络中的核心控制设备,不是它完成的功能为()。
张先生为了给女儿准备教育储蓄金,在未来的10年里,每年年底都申购10000元的债券型基金,年收益率为8%,则10年后张先生准备的这笔储蓄金为()元。(取近似值)
预计某股票年末每股税后利润为0.5元,若此时市场的平均市盈率为20倍,则该股票的发行价格理论上为()元。
清河王太傅辕固生者,齐人也。以治《诗》,孝景时为博士。与黄生争论景帝前。黄生曰:“汤、武非受命,乃弑也。”辕固生曰:“不然。夫桀、纣虐乱,天下之心皆归汤、武,汤、武与天下之心而诛桀、纣,桀、纣之民不为之使而归汤、武,汤、武不得已而立,非受命为何?”黄生曰:
()是一块超大规模的集成电路,是一台计算机的运算核心和控制核心,它的功能主要是解释计算机指令以及处理计算机软件中的数据。
A.条件(1)充分,但条件(2)不充分B.条件(2)充分,但条件(1)不充分C.条件(1)和条件(2)单独都不充分,但条件(1)和条件(2)联合起来充分D.条件(1)充分,条件(2)也充分E.条件(1)和条件(2)单独都不充分,条件(1)和条件(2
要设置在报表每一页的底部都输出的信息,需要设置()。
A-----Guardagainstdamp.J-----Openhere.B-----Handlewithcare.K-----Openindarkroom.C-----Keepaway
最新回复
(
0
)