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
2018-06-27
35
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/SzH7777K
0
大学英语六级
相关试题推荐
Forthispart,youareallowed30minutestowriteashortessaybasedonthepicturebelow.Youshouldfocusontheimpactofs
A、Theydon’tgotocollegerightafterhighschool.B、Theyspendtoomuchtimeinmiddleschool.C、Theyoncedroppedoutofcoll
A、Aphenomenonofagingfacebecauseoffacingcomputerforlong.B、Afeatureofscreen-shapefacebecauseofpeoplefollowingf
A、Thosewholiveinthevirtualworld.B、Thosewhohavetoworklonghours.C、Thosewhoareusedtoonlinetransactions.D、Those
GeorgeHerbertMeadsaidthathumansaretalkedintohumanity.Hemeantthatwegainpersonalidentityaswecommunicatewithot
Gulliverhasafriendwhorecentlygaveuphisjobtostudyfor"TheKnowledge",thenotoriouslydifficultprogrammethatLondo
Tsunamis[A]UpuntilDecemberof2004,thephenomenonoftsunamiwasnotonthemindsofmostoftheworld’spopulation.Tha
Webuybooks,andthentheywaitforustoreadthemDays,months,evenyears.Booksare【C1】______That’sOKforbooks,butnotf
秦始皇是中国历史上杰出的政治家、军事家。公元前221年,他统一中国,建立了历史上第一个统一的、多民族的、高度中央集权的(highlycentralized)国家——秦朝,并成为中国第一个皇帝,自称“始皇帝”。为加强统治,他实施了一系列的改革,如统一文字,
AstheworldexcitedlygreetedSnuppy,thefirstcloned(克隆)dog,commentatorscelebratedourcleverness.Manyfeelproudthato
随机试题
个体自我意识发展的开始时期是
A、甲硝唑B、碘酚C、复方碘甘油D、碘氧液E、复方氯己定治疗牙周炎的全身用药的药物是
甲型肝炎病毒(HAV)的主要传播途径是流行性乙型脑炎病毒的主要传播途径是
总长为3.2m,总宽为1.6m,总高为1.8m的微型汽车,其车辆构筑物横距应为()。
参数估计是依据样本信息推断未知的总体参数。()
所有基金绩效衡量指标均是事前衡量。( )
曹彬,字国华,真定灵寿人。父芸,成德军节度都知兵马使。彬始生周岁,父母以百玩之具罗于席,观其所取。彬左手持干戈,右手持俎豆,斯须取一印,他无所视,人皆异之。…………五年,使吴越,致命讫即还。私觌之礼,一无所受。吴越人以轻舟追遗之,至于数四,彬犹不
下列各句中,没有语病的一句是()。
认证(authentication)是防止()攻击的重要技术。
Agingbabyboomersaredeterminedtofighttheagingprocess.Theyspendmillionsofdollarsayearon【C1】________theyperceive
最新回复
(
0
)