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.
Answer: C

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.
Answer: C

4. Sound travels in air by a series of
compressions.
rarefactions.
Both of these.
None of these.
Answer: C

5. Sound travels in air by a series of
compressions.
rarefactions.
Both of these.
None of these.
Answer: C

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.
Answer: C

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.
Answer: C

8. Sound travels in
solids.
liquids.
gases.
All of these.
Answer: D

9. Sound travels in
solids.
liquids.
gases.
All of these.
Answer: D

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

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

12. The speed of sound varies with
amplitude.
frequency.
temperature.
All of these.
Answer: C

13. The speed of sound varies with
amplitude.
frequency.
temperature.
All of these.
Answer: C
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.
Answer: D

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

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

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

18. When sound undergoes refraction, it undergoes a change in
frequency.
wavelength.
speed.
intensity.
Answer: C

19. When sound undergoes refraction, it undergoes a change in
frequency.
wavelength.
speed.
intensity.
Answer: C

20. Sound can NOT be reflected. absorbed. diminished by interference.
None of these.
Answer: D

21. Sound can NOT be reflected. absorbed. diminished by interference.
None of these.
Answer: D
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.
Answer: D

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

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

25. Sound normally travels farther in air when the sound is
low frequency.
high frequency.
resonant.
low in energy.
Answer: A
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.
Answer: A

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

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

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

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

31. When the surface of a guitar is made to vibrate, we say it undergoes
forced vibration.
resonance.
refraction.
amplitude enhancement.
Answer: A
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.
Answer: B

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.
Answer: B
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.
Answer: B

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

36. The phenomenon of beats is the result of sound
destruction.
interference.
resonance.
amplification.
Answer: B

37. The phenomenon of beats is the result of sound
destruction.
interference.
resonance.
amplification.
Answer: B

38. When a 134-Hz tuning fork and a 144-Hz tuning fork are struck, the beat frequency is
more than 8 Hz.
Answer: D

39. When a 134-Hz tuning fork and a 144-Hz tuning fork are struck, the beat frequency is
more than 8 Hz.
Answer: D
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
Answer: B

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