首页
登录
职称英语
The prefix Mach is used to describe supersonic speed. It was named for Erns
The prefix Mach is used to describe supersonic speed. It was named for Erns
游客
2023-11-06
69
管理
问题
The prefix Mach is used to describe supersonic speed. It was named for Ernst Mach (1838-1916), a Czech-born Austrian physicist, who contributed to the study of sound. When twice the speed of sound, it is Mach 2. When it is near but below the speed of sound, its speed can be designated at less than Mach 1. for example, Mach 90. Mach is defined as "the ratio of the velocity of a rocket or a jet to the velocity of sound in the medium being considered."
When a plane passes the sound barrier-flying faster than sound travels’ listeners in the area hear thunderclaps, but the pilot of the plane does not hear them.
Sound is produced by vibrations of an object and is transmitted by alternate increase and decrease in pressure that radiate outward through a material media of molecules--somewhat like waves spreading out on a pond after a rock has been tossed into it.
The frequency of sound is determined by the number of times the vibrating waves undulate per second and is measured in cycles per second. The slower the cycle of waves, the lower the frequency. As frequencies increase, the sound is higher in pitch.
Sound is audible to human beings only if the frequency falls within a certain range. The human ear is usually not sensitive to frequencies of fewer than 20 vibrations per second, or more than about 20,000 vibrations per second--although this range varies among individuals. Anything at a pitch higher than the human ear can hear is termed ultrasonic.
Intensity, or loudness, is the strength of the pressure of these radiating waves and is measured in decibels. The human ear responds to intensity in a range from zero to 120 decibels. Any sound with pressure over 120 decibels is painful to the human ear.
The speed of sound is generally placed at 1088 feet per second at sea level at 32 degrees Fahrenheit. It varies in other temperatures and in different media. Sound travels faster in water than in air, and even faster in iron and steel. It travels a mile in 5 seconds in air, it does a mile under water in 1 second, and it travels through iron in 1/3 second. It travels through ice cold vapor at approximately 4,708 feet per second; ice-cold water, 4,938; granite, 12,960; hardwood, 12,620; brick, 11,960, glass. 16,410 to 19,690; silver, 8,658; gold, 5,717. [br] Decibel is
选项
A、the unit for measuring the4ntensity of sound.
B、the pressure of radiating waves.
C、the frequency of radiating waves.
D、the speed of sound.
答案
A
解析
根据第六段第一句“分贝是用来测量声音强度或大小的,即测量音量的单位”,故答案为A 。
转载请注明原文地址:http://tihaiku.com/zcyy/3164739.html
相关试题推荐
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErns
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Whenthetragicaccidenthappened,thetrainwasgoingatits______speed.A、ful
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
TheprefixMachisusedtodescribesupersonicspeed.ItwasnamedforErnst
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
Howlonghasthemansufferedfromthesymptomshedescribed?[br][originaltex
随机试题
WhoistelephoningMary?[br][originaltext]W:Hello.M:Hello.ThisisFred,Mar
There’sadirtylittlesecretinmanyAmericanhomes--couplesfightaboutthe
Therearesomestepsyoucantakeyourselftoavoidcatchingacold.Contrar
女性,50岁。上腹部持续性疼痛,向腰背部放射,伴呕吐12小时。既往有胆总管结石病
下列三叉神经损伤的临床特点中,错误的是A.颌面部骨折伤及眶上神经或眶下神经及其分
女性,55岁。50kg,2型糖尿病10年,头晕、乏力、食欲缺乏、呼吸困难1个月,
下列游客的要求中,如果导游不予满足就是违约的是( )。单选A.旅游合同中旅游者已
共用题干 一般资料:求助者,男性,24岁,某高校在读研究生。案例介绍:求助者毕
某商业公司非常重视安全文化建设,在安全文化建设方面投入了大量的人力物力,商场内的
轻中度低渗性脱水首先补充的液体是( )。A.5%碳酸氢钠 B.0.45%氯化
最新回复
(
0
)