首页
登录
职称英语
[originaltext] Objects that are vibrating make sounds.Rhythmic sound vibrati
[originaltext] Objects that are vibrating make sounds.Rhythmic sound vibrati
游客
2023-08-30
42
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.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 ultra- sound.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.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 hack 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.
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
What sounds Can humans hear?
转载请注明原文地址:https://tihaiku.com/zcyy/2971967.html
相关试题推荐
[originaltext]Earthquakesaresomethingthatmostpeoplefear.Thereareso
[originaltext]Manystudentstrytostudythewholenightanddonotsleepb
[originaltext]M:I’mEllanandIworkfortheStudentUnion.CanIaskyouafe
[originaltext]M:I’mEllanandIworkfortheStudentUnion.CanIaskyouafe
[originaltext]M:Goodafternoon.Iwonderifyoucouldgivemesomeinformation
[originaltext]M:Goodafternoon.Iwonderifyoucouldgivemesomeinformation
[originaltext]M:Goodafternoon.Iwonderifyoucouldgivemesomeinformation
[originaltext]Forcenturies,parrotshavebeenprizedpetsbecauseoftheir
[originaltext]Forcenturies,parrotshavebeenprizedpetsbecauseoftheir
[originaltext]Forcenturies,parrotshavebeenprizedpetsbecauseoftheir
随机试题
MostpeoplesaythattheUSAismakingprogressinfightingAIDS,butthey
GadgetswithaSportingChanceConsumerelectronics:
[originaltext]M:NowI’lltakesomequestions.W:Well,Mr.Brown,Ihaveaque
说明:假定你是胡斌,根据下列内容写一封邮件。发信人E—mail地址:hubin@163.com收信人E-mail地址:KPOHsales@—hotmail.
消防水泵自动巡检时,巡检周期应为7d,不得按随意设定。
A.1∶3∶1 B.2∶3∶1 C.2∶2∶1 D.1∶3∶3
赵先生46岁,身高170Cm,体重80kg,证券公司部门经理,在某健康管理中心要
具有神经肌肉阻滞作用,使虫体痉挛性麻痹的是()A:甲苯咪唑 B:伊维菌素
以下心些可以作为相对估值法的指标()。 Ⅰ.市盈率 Ⅱ.市净率 Ⅲ.销售
1.题目:语法教学 2.内容: 3.基本要求: (1)试讲时间约10分
最新回复
(
0
)