Bài hát: Listening Practice Through Dictation CD 4-07 - V.A

Unit 7 The White Noise Machine
W: And now ladies and gentlemen, the moment you
have al been waiting for. Here’s the winner of
this year’s science contest: Charles Moore!
Charles, tel everyone about your invention. M: Thank you! For the science contest this year, I’ve
invented a white noise machine. Let me explain what that is. Have you ever been kept awake at night because of the sound of traf ic, or people
talking, or loud music? These types of noise are
sometimes cal ed dark noise. Dark noise is made up of sounds that bother you so much that you
can’t concentrate on what you are doing. White noise is not exactly noise; in fact, white noise can’t be heard at al . White noise is made up of invisible waves of sound that reduce
the ef ects of dark noise by making sounds of
the opposite frequency. It’s like being in the ocean and seeing a large wave coming toward
you. It might knock you down. But if you could
send a wave, or many smal waves, toward the big wave, it wouldn’t be as powerful, because
the smal waves would hit it and reduce its size. My machine does this with sound. As a sound
enters the microphone, the machine determines
the sound’sfrequency. Then it makes a sound in the opposite frequency that cancels out the first sound.
I hope my machine wil give some peace and quiet to people living in noisy places. Thank you