The Magic of Sound[综合类职称英语教材]
Music is one of the most beautiful forms of artistic expressions ever invented.In movies and plays，music has an added function1:it not only moves people but also can shock people. Is it true that an ordinary musical instrument can be so powerful?
Our eardrums can withstand sound within 20 to 80 decibels.Once sound exceeds this limit2，even beautiful music will become ear-splitting noise3 and harm health.A strong blast of high sound can twist and break a solid iron sheet. 1
The noise from a plane’s engine is over 140 decibels.However，the sound of a flute is at most a few decibels. 2 It has been proven that people who have worked in an environment with a high sound intensity for a long time suffer varying degrees of heart disease or altered brain waves.
In movies，sometimes the hero can produce a sound that ordinary people can’t hear and only those who have the same ability can feel.In nature，there is actually sound that is beyond our hearing.In physics，the sound that exceeds 20,000 Hz is called ultrasonic. 3 It does no harm to health.
Sound less than 20 Hz is called infrasonic waves.When we move，the air will vibrate. 4 As the frequency of infrasonic waves is close to that of people’s internal organs4,infrasonic wave may cause resonance in human bodies. As a result，people’s vision may weaken and internal organs may rupture.However，whether an infrasonic wave can be used as a weapon depends on its intensity5.If its intensity is very low，it won’t damage internal organs or a person’s health. 5 When wind blows at a force of 3 or 4 over the sea6,it will produce infrasonic waves of several decibels.Only typhoons can produce infrasonic waves of over 100 decibels.At present，scientists can only produce infrasonic weapons in the lab with the help of advanced scientific tools and powerful electric power.
词汇:
eardrum n.耳膜
infrasonic adj.次声(波)的
twist v.使卷曲，使扭曲
flute n.长笛
Hz = hertz n.赫兹
ultrasonic adj.超声波的 n.超声波
withstand v.抵挡，经受住
decibel n.分贝
resonance n.共振
rupture n.破裂 v.(使)破裂
typhoon n.台风
注释：
1. an added function：另加的一种功能
2. Once sound exceeds this limit：一旦声音超过了这个界限。once是时间状语从句的连词。如： Once you have learned how to swim，you will love this sport.一旦你学会了游泳，你会爱上这一运动的。
3. ear-splitting noise：震耳欲聋的噪音
4. As the frequency of infrasonic waves is close to that of people’s internal organs：由于次声波的频率接近于人体内部器官的频率。that指代前面的frequency。
5. However，whether an infrasonic wave can be used as a weapon depends on its intensity：但是，次声波能否用作武器取决于次声波的强度。whether an infrasonic wave can be used as a weapon是从句，用作句子的主语。
6. When wind blows at a force of 3 or 4 over the sea：当海面上吹起3—4级风的时候
练习:
A High sound of 150 decibels can kill a healthy rat.
B The vibration of air can produce infrasonic waves.
C We cannot play high-pitched music with ordinary musical instruments.
D If the intensity of infrasonic wave exceeds 160 decibels，it is extremely harmful.
E Dolphins，whales and bats can make such high-frequency sound.
F Therefore，the sound of ordinary musical instruments cannot harm your health.
答案：1.A 2.F 3.E 4.B 5.D