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
2019-03-17
31
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://kaotiyun.com/show/gZH7777K
0
大学英语六级
相关试题推荐
A、Theeffectsofinterventionstoage5areasevidentasthosetoage3.B、Theeffectsofinterventionstoage5aremoreevide
Mostofusareacutelyawareofhowmuchmobiledataweconsumeonourphonesandtablets.That’sbecauseAmericansarelargely
A、Itisthecentreoftheworld.B、Itisnoteasytoreach.C、Ithasnoroomforlies.D、Itisbrightlikethesun.C
A、Carbondioxideemissions.B、ElNinoevent.C、Airpollution.D、Climatechange.A
A、Givethestudentstheorientationpacks.B、Handoverthekeystothestudents.C、Answerthestudents’questions.D、Guidethes
AstheworldexcitedlygreetedSnuppy,thefirstcloned(克隆)dog,commentatorscelebratedourcleverness.Manyfeelproudthato
A、Itmadepeoplehappier.B、Itdidmoreharmthangood.C、Itincreasedrisks.D、Itmadepeoplesick.B演讲人在介绍完自己的职业后,用转折句对过去十年的工作
Childrenwholivenearamainroadareingreaterdangerofcatchingpneumonia(肺炎)becausepollutionfrompassingtrafficdamag
HowtoDuckCabinFeversandOtherAchesonaPlane?[A]Onthefirstlegofthisseason’sholidaytraveltour,Ihadthedeligh
随机试题
在FlashMX和Firework进行颜色导入导出时,可以从外部的ACT文件导入渐变色。
如何进行焊缝的金相组织检验?
法国广播电视体制的演变历程。
患儿,男,4个月,舌系带粗短、附着较高,伸舌时舌尖部呈“W”形目前的治疗是
可致肝细胞损害的药有
在运用环境影响的效益,费用评价方法时,根据补偿环境恶化的费用来确定环境价值,通常运用的方法为()。
企业资源计划的英文简称是()。
托运人必须办理保价运输。()
投资规模是指一定时期内用货币表现的为形成资产而投入的活劳动和物化劳动产量。()
______resultsin"Acidrain"?______couldcontributetoglobalwarming?
最新回复
(
0
)