四六级备考 | 听力天天练215（附原文与解析）
关注回复关键字“福利”，免费送你优质英文有声读物！
公众平台对话框，回复四六级，进打卡群交流，分享资料
四六级马上就要考试了，小伙伴们油吧！
四六级备考 | 20天四级单词组队打卡合集（附音频）
四六级备考 | 听力天天练50集合集
四六级备考 | 听力天天练100集合集
四六级备考 | 听力天天练150集合集
四六级备考 | 听力天天练200集合集
四六级备考 | 听力天天练250合集（附原文与解析）
四六级备考 | 听力天天练251（附原文与解析）
四六级备考 | 听力天天练252（附原文与解析）
四六级备考 | 听力天天练253（附原文与解析）
四六级备考 | 听力天天练254（附原文与解析）
四六级备考 | 听力天天练255（附原文与解析）
四六级备考 | 听力天天练256（附原文与解析）
四六级备考 | 听力天天练257（附原文与解析）
四六级备考 | 听力天天练258（附原文与解析）
四六级备考 | 听力天天练259（附原文与解析）
四六级备考 | 听力天天练260（附原文与解析）
四六级备考 | 听力天天练261（附原文与解析）
四六级备考 | 听力天天练262（附原文与解析）
四六级备考 | 听力天天练263（附原文与解析）
四六级备考 | 听力天天练264（附原文与解析）
四六级备考 | 听力天天练265（附原文与解析）
四六级备考 | 听力天天练266（附原文与解析）
四六级备考 | 听力天天练267（附原文与解析）
四六级备考 | 听力天天练268（附原文与解析）
四六级备考 | 听力天天练269（附原文与解析）
四六级备考 | 听力天天练270（附原文与解析）
四六级备考 | 听力天天练271（附原文与解析）
四六级备考 | 听力天天练272（附原文与解析）
四六级备考 | 听力天天练273（附原文与解析）
四六级备考 | 听力天天练274（附原文与解析）
打卡方法：留言处写下答案，留言格式：昵称+天数，e.g 爱酱-Day
CET4&6听力训练
29.
A. The quicker it vibrates, the greater the frequency of sound it produces.
B. The slower it vibrates, the higher the frequency of sound it produces.
C. The quicker it vibrates, the lower the frequency of sound it produces.
D. The frequency of sound it produces is not in proportion to the speed it vibrates.
30.
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.
31.
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.
合集收藏
备考专辑：英专听力50篇 & 20天四级单词 & 60篇高分范文 & 学术写作40集 & 哈佛大学写作
语音单词：美音发音视频教程 & 英音发音视频教程 & 名师课堂100集
新闻英语：VOA标准 & VOA慢速 & BBC新闻 & 18BBC地道英语
歌曲TED: 听歌学英语 & TED合集 & 18年歌曲合集 & 19年歌单
美文故事: 双语美文30篇 & 有声双语48篇 & 听名著学英语 & 图说英文
名字外教：男生版 & 女生版 & 搞笑版 & 命运版 & 外教课310合集 & 每日听写200集
微信公众号改版，订阅号消息不再按时间排序，为了防止迷路，希望小可爱们可以动动小小手点个“在看”或者将“小芳老师”添加到★“星标”☆中！让系统知道这是你喜欢看的公众号，这样我们就可以一直就可以永远幸福在一起啊！
答案解析
A C B
听力原文
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. [29]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. [30]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.
[31]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. [31]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. Dolphins' ultrasound ability is so sensitive that they can detect small fish from 10 feet away.
29. What is the relationship between the vibration of an object and the frequency of its sound?
正确答案：A解析：细节题。短文提到，物体振动得越快，它制造的声音频率就越高。A为原文中the more...the greater结构的同义表达，故为正确答案。B与C意思相同，可同时排除；D明显与原文内容相冲突。
30. What sounds can humans hear?
正确答案：C解析：细节题。文中提到，人类可以听见频率在20赫兹到2万赫兹之间的声音。由此可知，C为正确答案。
31. According to the speaker, what is the phenomenon of echolocation?
正确答案：B解析：细节题。文中提到，用声音来找或看东西被称为“回声定位法”。之后，短文以海豚为例说明“回声定位法”：海豚会发出尖利的声音，这种声音会撞击到它周围的任何物体，然后通过声波形式再传回到海豚处。通过这种方法，海豚可以找到离自己10英尺以内的小鱼。蝙蝠只是利用回声定位原理“找到”食物，但并非caught或ate，所以可排除强干扰项A。
特别声明：以上内容(如有图片或视频亦包括在内)为自媒体平台“网易号”用户上传并发布，本平台仅提供信息存储服务。
Notice: The content above (including the pictures and videos if any) is uploaded and posted by a user of NetEase Hao, which is a social media platform and only provides information storage services.
