Chapter 20

1. Chapter 20 Sound

2. The sound waves that most humans cannot hear are • infrasonic. • ultrasonic. • Both of these. • None of the above, for young people can hear both.

3. The sound waves that most humans cannot hear are • infrasonic. • ultrasonic. • Both of these. • None of the above, for young people can hear both.

4. Sound travels in air by a series of • compressions. • rarefactions. • Both of these. • None of these.

5. Sound travels in air by a series of • compressions. • rarefactions. • Both of these. • None of these.

6. The vibrations set up in a radio loudspeaker have the same frequencies as the vibrations • in the electric signal feeding the loudspeaker. • that produce the sound you hear. • Both of these. • None of these.

7. The vibrations set up in a radio loudspeaker have the same frequencies as the vibrations • in the electric signal feeding the loudspeaker. • that produce the sound you hear. • Both of these. • None of these.

8. Sound travels in • solids. • liquids. • gases. • All of these.

9. Sound travels in • solids. • liquids. • gases. • All of these.

10. In which of these materials does sound travel fastest? • Air • Water • Steel • All the same at the same temperature

11. In which of these materials does sound travel fastest? • Air • Water • Steel • All the same at the same temperature

12. The speed of sound varies with • amplitude. • frequency. • temperature. • All of these.

13. The speed of sound varies with • amplitude. • frequency. • temperature. • All of these. Explanation: Although loudness varies with amplitude, and pitch varies with frequency, speed is not influenced by amplitude nor frequency. A listener in the back row at a concert would find music confusing if sound of different frequencies reached the ear at different times.

14. The loudness of a sound is most closely related to its • frequency. • period. • wavelength. • amplitude.

15. The loudness of a sound is most closely related to its • frequency. • period. • wavelength. • amplitude.

16. Sound made to undergo reverberation is sound that is • sympathetically vibrating. • varying in tone. • multiply reflected. • refracted.

17. Sound made to undergo reverberation is sound that is • sympathetically vibrating. • varying in tone. • multiply reflected. • refracted.

18. When sound undergoes refraction, it undergoes a change in • frequency. • wavelength. • speed. • intensity.

19. When sound undergoes refraction, it undergoes a change in • frequency. • wavelength. • speed. • intensity.

20. Sound can NOT be • reflected. • absorbed. • diminished by interference. • None of these.

21. Sound can NOT be • reflected. • absorbed. • diminished by interference. • None of these. Comment: Sound, like any wave, can undergo all of these!

22. Sensing an invisible object by way of ultrasound is used by • bats. • dolphins • medical doctors. • All of these.

23. Sensing an invisible object by way of ultrasound is used by • bats. • dolphins • medical doctors. • All of these.

24. Sound normally travels farther in air when the sound is • low frequency. • high frequency. • resonant. • low in energy.

25. Sound normally travels farther in air when the sound is • low frequency. • high frequency. • resonant. • low in energy. Explanation: Hence the low tone of fog horns.

26. A factory floor vibrates, and as a result you vibrate when standing on the floor. This is • forced vibration. • resonance. • refraction. • diffraction.

27. A factory floor vibrates, and as a result you vibrate when standing on the floor. This is • forced vibration. • resonance. • refraction. • diffraction.

28. When you tap various objects, they produce characteristic sounds that are related to • wavelength. • amplitude. • period. • natural frequency.

29. When you tap various objects, they produce characteristic sounds that are related to • wavelength. • amplitude. • period. • natural frequency.

30. When the surface of a guitar is made to vibrate, we say it undergoes • forced vibration. • resonance. • refraction. • amplitude enhancement.

31. When the surface of a guitar is made to vibrate, we say it undergoes • forced vibration. • resonance. • refraction. • amplitude enhancement. Comment: The sound may be enhanced, but it is the surface of the guitar that undergoes forced vibration.

32. When an object is set vibrating by a wave having a frequency that matches the natural frequency of the object, what occurs is • forced vibration. • resonance. • refraction. • amplitude enhancement.

33. When an object is set vibrating by a wave having a frequency that matches the natural frequency of the object, what occurs is • forced vibration. • resonance. • refraction. • amplitude enhancement. Comment: Resonance, rather than amplitude enhancement, is the better answer.

34. Noise-canceling devices such as jackhammer earphones make use of sound • destruction. • interference. • resonance. • amplification.

35. Noise-canceling devices such as jackhammer earphones make use of sound • destruction. • interference. • resonance. • amplification.

36. The phenomenon of beats is the result of sound • destruction. • interference. • resonance. • amplification.

37. The phenomenon of beats is the result of sound • destruction. • interference. • resonance. • amplification.

38. When a 134-Hz tuning fork and a 144-Hz tuning fork are struck, the beat frequency is • 2 Hz. • 6 Hz. • 8 Hz. • more than 8 Hz.

39. When a 134-Hz tuning fork and a 144-Hz tuning fork are struck, the beat frequency is • 2 Hz. • 6 Hz. • 8 Hz. • more than 8 Hz. Explanation: The beat frequency is the difference between the two, 10 Hz (which is more than 8 Hz).

40. When your radio set is tuned to an incoming radio signal, what occurs? • Forced vibration • Resonance • Refraction • Diffraction

41. When your radio set is tuned to an incoming radio signal, what occurs? • Forced vibration • Resonance • Refraction • Diffraction