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
A、A bat caught the insect in midair and ate it. B、Dolphin’ s clicking sounds bounced off the fish and back to it. C、A person hea
A、A bat caught the insect in midair and ate it. B、Dolphin’ s clicking sounds bounced off the fish and back to it. C、A person hea
admin
2019-09-13
46
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. [23] 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. [24] 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. [25-1] Using sound to find or “see” things is called echolocation. Another animal that uses ultrasound is the dolphin. Dolphin scan hear sounds up to about 150,000 hertz. Dolphins use sound waves to find food underwater. [25-2] 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. [25-3] Dolphins’ ultrasound ability is so sensitive that they can detect small fish from 10 feet away.
23.What is the relationship between the vibration of an object and the frequency of its sound?
24.What sounds can humans hear?
25.According to the speaker, what is the phenomenon of echolocation?
选项
A、A bat caught the insect in midair and ate it.
B、Dolphin’ s clicking sounds bounced off the fish and back to it.
C、A person heard an echo when he shouted into the valley.
D、A dog heard his owner’ s whistle because he used ultrasound.
答案
B
解析
转载请注明原文地址:https://kaotiyun.com/show/GHW7777K
0
大学英语六级
相关试题推荐
BabyBoomersAreKillingThemselvesatanAlarmingRate[A]Ithaslongheldtruethatelderlypeoplehavehighersuiciderates
BabyBoomersAreKillingThemselvesatanAlarmingRate[A]Ithaslongheldtruethatelderlypeoplehavehighersuiciderates
BabyBoomersAreKillingThemselvesatanAlarmingRate[A]Ithaslongheldtruethatelderlypeoplehavehighersuiciderates
BabyBoomersAreKillingThemselvesatanAlarmingRate[A]Ithaslongheldtruethatelderlypeoplehavehighersuiciderates
Somesayitisevidentthatcomputerscandamageaperson’seyesight.Sincethepopularityofcomputersbegantoskyrocket,ther
Somesayitisevidentthatcomputerscandamageaperson’seyesight.Sincethepopularityofcomputersbegantoskyrocket,ther
Somesayitisevidentthatcomputerscandamageaperson’seyesight.Sincethepopularityofcomputersbegantoskyrocket,ther
Somesayitisevidentthatcomputerscandamageaperson’seyesight.Sincethepopularityofcomputersbegantoskyrocket,ther
A、Sentastorytothelocalnewspaper.B、ThrewasmallThanksgivingparty.C、Bakedsomecookiesasapresent.D、Wroteapersonal
MarieCuriewasthefirstfemaleprofessoratSevres,acollegeforgirlswhowantedtoteachhighereducation.Thesetwenty-yea
随机试题
熔滴过度主要靠:熔滴重力、表面张力、电磁压缩力、斑点压力(辉点压力)、等离子流力及电弧吹力等。
在政府系列中,专司各级国家机关干部管理职能的部门是()
A.下唇歪斜B.鼓腮障碍C.额纹消失D.眼睑不能闭合E.伸舌时偏向患侧舌下神经损伤表现为
对风湿性心脏病最具有诊断意义的病变是
关于综合成本的分析方法,下列说法正确的是()。
纳税人建造普通标准住宅出售,增值额超过扣除金额20%的,应按全部增值额计算缴纳土地增值税。()
催办的形式有()。
区分不同性质国家的根据是()。
根据占有人是否具有所有的意思,占有可以分为()
为使文本框具有初始值“VB”,在设计阶段正确的操作是
最新回复
(
0
)