首页
登录
职称英语
[originaltext] Objects that are vibrating make sounds.Rhythmic sound vibrati
[originaltext] Objects that are vibrating make sounds.Rhythmic sound vibrati
游客
2024-05-07
59
管理
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.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.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 ultra- sound.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.Using sound to find or“see” things is called echolocation.Another animal that uses ultrasound is the dolphin.Dolphins can hear sounds up to about 150,000 hertz.Dolphins use sound waves to find food underwater.They make clicking sounds that hit whatever is around them and then bounce hack to the dolphins.Dolphins can send as many as 2,000 clicks per second.Dolphins’ ultrasound ability is so sensitive that they can detect small fish from 10 feet away.
选项
A、Those with frequencies lower than 20 hertz.
B、Those with frequencies about 21,000 hertz.
C、Those with frequencies lower than 20,000 hertz.
D、Those with frequencies higher than 20,000 hertz.
答案
C
解析
What sounds Can humans hear?
转载请注明原文地址:http://tihaiku.com/zcyy/3588231.html
相关试题推荐
[originaltext]Thehomeisthecentralfocusofmostyoungpeople’slivesin
[originaltext]Thehomeisthecentralfocusofmostyoungpeople’slivesin
[originaltext]Thehomeisthecentralfocusofmostyoungpeople’slivesin
[originaltext]Hello,IamHarrietSmith.AstheeditorofTheVoice,I’dli
[originaltext]Hello,IamHarrietSmith.AstheeditorofTheVoice,I’dli
[originaltext]Objectsthatarevibratingmakesounds.Rhythmicsoundvibrati
[originaltext]M:You’regoingtoSoutheastAsiancountriesforaholidaysoon,
[originaltext]M:You’regoingtoSoutheastAsiancountriesforaholidaysoon,
[originaltext]M:You’regoingtoSoutheastAsiancountriesforaholidaysoon,
[originaltext]Forcenturies,parrotshavebeenprizedpetsbecauseoftheir
随机试题
[originaltext]DuringtheChristmasshoppingrushinLondon,aninteresting
根据《计算机软件保护条例》的规定,当软件()后,其软件著作权才能得到保护。A
施工单位承接一项水泥厂安装工程项目,进行到第8个月时,施工单位对前7个月的工作进
关于军团菌的血清分型叙述正确的是A.根据O抗原将嗜肺军团菌分15个血清型B.根据
物业管理的基本特征包括()A:产业化 B:社会化 C:专业化 D:标准化
手阳明大肠经入A.下齿 B.目 C.舌本 D.上齿
既可直刺、深刺,又可针刺放血的腧穴是A.肩井 B.承泣 C.瞳子髎 D.委
下列关于三类工程综合平衡的论述,正确的是()。A.应围绕关键线路的关键工程组织
老年人肠扭转最常见的部位是( )。A.横结肠 B.十二指肠 C.乙状结肠
妨碍铁剂在肠道吸收的物质是A.维生素C B.果糖 C.食物中高磷、高钙、鞣酸
最新回复
(
0
)