"Sound" (текст с послетекстовыми заданиями для изучения профессионального модуля)

Sound

Sound travels through the air in the form of waves.

Sound waves are sent out from any object that vibrates or swings to and fro. If there are 20 to 20,000 swings each second, we can hear a sound.

The faster a thing vibrates, the higher the pitch of the tone it produces. The pitch of the tone also depends on the size and shape of the vibrating object.

If you strike the side of an empty glass, it vibrates and gives off a musical tone. If water is poured into the glass, it gives a different tone because the part that can vibrate freely is now changed in size.

Try this experiment. Take eight drinking-glasses and pour different amounts of water into them. You will be able to play ah eight-tone scale and simple melodies on them. But it will need a bit of experimenting to get the right amount of water.

When we strike a bell or a gong, the metal vibrates and the vibration produces sound waves in the air.

Try another experiment. Take a table-spoon and a piece of string, five feet long. Tie the spoon at the handle in the middle of the string. Hold the ends of the string to your ears with your fingers and let the-spoon hang freely. Now swing it a little and let it strike against some hard object. The sound you will hear is surprisingly loud. The loudness can be explained by the fact that the vibrations come directly to your ears through the string and not through the air.

Sound propagates not only in the air but also in other bodies. Different bodies conduct sound in different ways. Most metals, wood, gases and also liquids are good sound conductors, soft and porous bodies are poor conductors. Thus sound propagates in all resilient bodies, solid, liquid and gaseous; but it cannot propagate in a vacuum.

Vocabulary:

1. to and fro — туда и обратно.

2. The faster a thing vibrates, the higher the pitch of the tone it pro­duces. — Чем чаще вибрирует предмет, тем выше частота тона.

3. Hold the end of the string to your ears with your fingers and let the

spoon hang freely. — Концы веревки прижмите к ушам, а ложка пусть болтается.

4. let it strike against some hard objects — пусть она ударится о что-то твердое.

5. soft and porous bodies are poor conductors — мягкие и пористые тела – плохие проводники (звука).

6. sound – звук

7. wave – волна

8. to vibrate – вибрировать

9. to depend on – зависеть от

10. shape – форма

11. to strike – ударять

12. empty – пустой

13. string – бечевка

14. to conduct – проводить

15. liquid – жидкость

16. to propagate – передавать на расстояние через среду

17. resilient – упругий, эластичный

Answer the questions:

1. Where does sound travel through?

2. Are sound waves sent out from any object that vibrates or swings to and fro?

3. What the pitch of the tone also depends on?

4. When does an empty glass vibrate and give off a musical tone?

5. When does it give a different tone?

6. What will happen if we strike a bell or a gong?

7. How can the loudness be explained?

8. Can sound propagate not only in the air?

9. Different bodies conduct sound in different ways, don’t they?

10. What bodies are good sound conductors?

11. What bodies are poor sound conductors?

12. Can sound propagate in a vacuum?