High-Q | 9 סימולציה

31

סימולציה מס' 9

פרק שני

– אנגלית

Text II (Questions 18-22)

One important measure of the way sound is heard is the frequency of the sound. You can feel some sounds as well as hear them with the ears. For example, it’s possible to feel a vibration in your chest when the speakers in some powerful stereo systems are producing very low frequencies. Similarly, the low rumble of underground subway trains can be felt through the floors of buildings overhead at street level. 5 The frequency of a sound wave is measured by means of a unit called “hertz”. Sound occurs when the air vibrates. If the air vibrates slowly, it has a low number of cycles per second, or hertz, and produces a deep sound. A fast vibration has a higher frequency, and produces a high-pitched sound. 10 about 20 hertz to highs of about 20,000 hertz. The speaking frequency for most people falls into the 500-2,000 hertz range. The ear is most sensitive to sounds that occur in the 1,000 4,000 hertz range. Because the ear is more sensitive to some frequencies than others, it is more susceptible to damage in certain ranges of frequencies than others. The most sensitive area 15 is around 4,000 hertz. If you were exposed to a collection of all frequencies played simultaneously - this is known as “white noise” - the damage to your hearing would occur first at 4,000 hertz. Since most loud sounds, such as explosions, consist of white noise, you can see how hearing loss can easily happen. 20 as 16 hertz and, in some cases, as high as 40,000 hertz. But the ability to hear so acutely begins to drop after about age 10. The human ear is capable of responding to a wide range of frequencies, from a low of Hearing is at its best during childhood, when it is possible to hear frequencies as low

Questions

18. According to the first paragraph, sounds which can be detected by means other than ears alone -

(1) occur mainly underground (2) vibrate fast through the air (3) are low in frequency (4) are called white noise

19. We can infer from the passage that when the air is still -

(1) a high frequency sound occurs (2) a very low pitched noise occurs (3) the sound travelling through the air cannot be measured in hertz (4) no sound occurs

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