第二篇：

　　The Magic of Sound

　　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 t0 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. High sound of 150 decibels can kill a healthy rat.

　　The noise from a plane’s engine is over 140 decibels.However,the sound of a flute is at most a few decibels. Therefore, the sound of ordinary musical instruments cannot harm your health. 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. Dolphins, whales and bats can make such high—frequency sound. It does no harm to health.

　　Sound less than 20Hz is called infrasonic waves. When we move, the air will vibrate. The vibration of air can produce infrasonic waves. 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 intemal organs or a person's Health. If the intensity of infrasonic wave exceeds l60 decibels, it is extremely harmful. 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 l00 decibels. At present, scientists can only produce infrasonic weapons in the lab with the help of advanced scientific tools and powerful electric power.

　　36. What would be the best title of the passage?

　　A. The power of music.

　　B. The harms of noises.

　　C. The magic of sound.

　　D. The discovery of infrasonic waves.

　　37. What does the author say about music?

　　A. It may be harmful to people’s health.

　　B. It always cheers people up.

　　C. It is very often difficult to understand.

　　D. It sounds better when it is loud enough.

　　38. It is true that the sound

　　A. of nature is the most beautiful.

　　B. over 80 decibels is harmful to people.

　　C. of high intensity benefits animals.

　　D. in movies is pleasing to the ear.

　　39. An ultrasonic sound

　　A. is very loud.

　　B. does harm to people’s health.

　　C. cannot be heard by people.

　　D. is produced by the hero in movies.

　　40. It can be found from the last paragraph that infrasonic waves

　　A. are harmless to people’s health.

　　B. exist in people’ internal organs.

　　C. can be used as deadly weapons.

　　D. can improve eyesight.