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
78
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
A、Itwillgoup.B、Itwillcomedown.C、Itwillgoupanddown.D、Itwillstaythesame.A①由选项可知,本题问It在未来的发展趋势。It在此处指代的是thepric
中国是一个有56个民族的大国。不同的民族有不同的婚俗。中国传统婚礼包括6个必备步骤,即说媒、定亲、聘礼(betrothalgifts)、迎娶、拜堂(三鞠躬)、喝交杯酒(wedlockwine)。如今典型的中国婚礼如下进行:新人订婚后,接下来就是挑选吉(
PresidentBarackObama’spicktoheadtheEnvironmentalProtectionAgency(EPA),LisaJackson,hasspent20yearsasanenvironme
A、Itismadeaccordingtorealpeople.B、Itassesseschangesofproperties.C、Itinvolvesdifferentfacialfeatures.D、Itismad
A、Bytakingpartinspecificactivities.B、Bydoingmoreexercise.C、Bygivingbookstoyourfriends.D、Byeatingnutritiousfoo
A、Wemaygetsympathyfromfriends.B、Wemayrelievesomeofourstress.C、Wemaygetanegativereputation.D、Wemaybelaughed
A、Thevolumeofbloodandbloodpressurewilldropwithoutit.B、Itisthebasefordigestionandabsorptionoffood.C、Itisre
A、Nothingbutthebonesoftheswanshasbeenfound.B、ThefirstremainsofaswanturnedupjustbeforeChristmas.C、Stealings
A、Itismoreimportantthanmoney.B、Peoplewerebornwithit.C、Peopleuseittogetthroughdifficulties.D、Itcanhealtheso
OnSaturday,BexarCountyDigitalLibrary—a$2.4million,4,000-square-footspacelocatedonthesouthsideofSanAntonio—opens
随机试题
AsValentine’sDayapproaches,manysinglepeoplebegintofeelalittlesorryforthemselves.Onaday【C1】________bycouples,
A.可复性疝B.Littre疝C.Ricllter疝D.绞窄性疝E.滑疝左腹股沟疝数月,反复脱出,平卧即消失,诊断为
根据上述情景判断其出血量为( )。王某出血后易诱发( )。
根据我国合同法的规定,技术进出口合同提起诉讼或者申请仲裁的期限为()。
(二) 迅辉制药股份公司主要生产健骨消痛丸,公司法定代表人陆某指令保管员韩某采用不登记入库、销售人员打白条领取产品的方法销售,逃避缴税65万元。迅辉公司及陆某以逃税罪
当事人可以自由选择一种形式即可成立的法律行为,称为()。
一些教师针对学生做错了习题而给予他们惩罚,这种做法违背了惩罚的()。
政府出台新规定。基层领导下乡调研要隐瞒身份。并采用记者的身份,你怎么看?
萧条∶欣欣向荣
下列叙述中正确的是
最新回复
(
0
)