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、Those with frequencies lower than 20 hertz. B、Those with frequencies about 21,000 hertz. C、Those with frequencies from 20 hert
A、Those with frequencies lower than 20 hertz. B、Those with frequencies about 21,000 hertz. C、Those with frequencies from 20 hert
admin
2019-09-13
44
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、Those with frequencies lower than 20 hertz.
B、Those with frequencies about 21,000 hertz.
C、Those with frequencies from 20 hertz to 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:https://jikaoti.com/ti/mSIFFFFM
0
大学英语六级
相关试题推荐
BabyBoomersAreKillingThemselvesatanAlarmingRate[A]Ithaslongheldtruethatelderlypeoplehavehighersuiciderates
BabyBoomersAreKillingThemselvesatanAlarmingRate[A]Ithaslongheldtruethatelderlypeoplehavehighersuiciderates
MarieCuriewasthefirstfemaleprofessoratSevres,acollegeforgirlswhowantedtoteachhighereducation.Thesetwenty-yea
MarieCuriewasthefirstfemaleprofessoratSevres,acollegeforgirlswhowantedtoteachhighereducation.Thesetwenty-yea
MarieCuriewasthefirstfemaleprofessoratSevres,acollegeforgirlswhowantedtoteachhighereducation.Thesetwenty-yea
MarieCuriewasthefirstfemaleprofessoratSevres,acollegeforgirlswhowantedtoteachhighereducation.Thesetwenty-yea
A、Thosewithfrequencieslowerthan20hertz.B、Thosewithfrequenciesabout21,000hertz.C、Thosewithfrequencieslowerthan2
随机试题
北宋第一个专力填词的作家是________,他是北宋________词派的早期代表。他使慢词发展成为与小令双峰并峙的一种成熟的文学样式。他的词多从生活汲取素材,在当时________阶层中传唱最盛,有作品集《乐章集》传世。
食管癌的主要转移途径是()
椭圆囊和球囊的适宜刺激是
施工现场平面布置图不包括以下哪项内容?()
首倡“教师作为研究者”的学者是()。
2016年上半年,北京市六大高端产业功能区(以下简称“六高”)规模以上法人单位实现收入28811.4亿元,占全市的比重超过五成(51.5%),较上年同期提高2.9个百分点。其中,工业实现收入占全市工业的比重超过六成(62.4%),较上年同期提高2.3个
网络操作系统为支持分布式服务功能,提出了一种新的网络资源管理机制,即( )
需求分析阶段的任务是确定()。
PASSAGEONE
A、OnlystudentsatNorthCollegecanjoinit.B、Themancanfillouttheapplicationformonline.C、Themancanonlyborrow8it
最新回复
(
0
)