首页
登录
职称英语
[originaltext] Objects that are vibrating make sounds. Rhythmic sound vibrat
[originaltext] Objects that are vibrating make sounds. Rhythmic sound vibrat
游客
2023-09-04
44
管理
问题
Objects that are vibrating make sounds. Rhythmic sound vibrations produce sound waves which travel in every direction. The frequency of a sound is the number of waves that pass a given point each second. [29]The more rapidly an object vibrates, the greater the frequency of sound it makes. Frequency is measured in hertz. One hertz equals one sound wave per second. The frequency of sound determines the degree of highness or lowness of the sound. A high-pitched sound has a higher frequency than a low-pitched sound. Humans hear sounds that have frequencies from about 20 hertz to 20,000 hertz. Sound with a frequency higher than 20,000 hertz is called ultrasound which is too high-pitched for humans to hear. However, many animals can hear ultrasound. Bats can hear higher sounds than any other animal. Some can hear up to 210,000 hertz. Bats send out lots of high-pitched squeaks and then listen to the echoes bouncing off things like insects. The shorter the time interval between the squeak and the echo, the closer they are to the insect. [31]Using sound to find or "see" things is called echolocation. Another animal that uses ultrasound is the dolphin. Dolphins can hear sounds up to about 150,000 hertz. Dolphins use sound waves to find food underwater. They make clicking sounds that hit whatever is around them and then bounce back to the dolphins. Dolphins can send as many as 2,000 clicks per second. Dolphins’ ultrasound ability is so sensitive that they can detect small fish from 10 feet away.
Questions 29 to 31 are based on the conversation you just heard.
29. What is the relationship between the vibration of an object and the frequency of its sound?
30. What sounds can humans hear?
31. According to the speaker, what is the phenomenon of echolocation?
选项
A、Those with frequencies lower than 20 hertz.
B、Those with frequencies about 21,000 hertz.
C、Those with frequencies lower than 20,000 hertz.
D、Those with frequencies higher than 20,000 hertz.
答案
C
解析
转载请注明原文地址:http://tihaiku.com/zcyy/2984216.html
相关试题推荐
[originaltext]Fortwomonthsafterhestartedthewebsitedigg.com,KevinR
[originaltext]Fortwomonthsafterhestartedthewebsitedigg.com,KevinR
[originaltext]W:Hi,Tom,Ihaven’tseenyouinawhile.Whatseemstobethep
[originaltext]W:Hi,Tom,Ihaven’tseenyouinawhile.Whatseemstobethep
[originaltext]W:IknowyourcompanywasoneofthebiggestAmericancorporatio
[originaltext]W:IknowyourcompanywasoneofthebiggestAmericancorporatio
[originaltext](32)Whydowecry?Canyouimaginelifewithouttears?Notonly
[originaltext]Lifestyleisthewayapersonlives:itincludeswork,leisuretim
[originaltext]Lifestyleisthewayapersonlives:itincludeswork,leisuretim
[originaltext]Whetherornotvegetarianismshouldbeadvocatedforadults,(26)i
随机试题
Youmustremembernotto______fromthepointwhenyouwriteanessay.A、revolveB
Inanefforttosustaincommercialandrecreationalfishingforthenextsev
(1)JoanofArcwouldbeproud.EdithCresson,France’sfirstwomanPrimeMin
AnewstudyfromtheUniversityofNewSouthWaleshasdiscoveredthatdurin
线性光束感烟探测器按照说明书提供的方法模拟火警,探测器应发出火灾报警信号,并点亮
若f(x)为[a,b]上的连续函数,()A..小于0 B.大于0 C.等于0
测靛基质用的蛋白胨,含有大量的A.酪氨酸 B.精氨酸 C.鸟氨酸 D.苯丙
制定精神药品年度生产计划的部门为A.国务院药品监督管理部门 B.国务院卫生行政
()是税收规划最基本的原则,是税收规划与偷税漏税区别开来的根本所在。A:规划性原
如果用预置小数位数的方法输入数据时,当设定小数是“2”时,输入56789表示()
最新回复
(
0
)