Sound W.S.
1. Two major classes of waves are longitudinal and transverse. Sound waves are __________.
longitudinal
transverse
2. The frequency of a sound signal refers to how frequently the vibrations occur. A high-frequency
sound is heard at a high_____________.
pitch
wavelength
speed
The sketch below shows a snap shot of the compressions and rarefactions of the air in a tube as the
sound moves toward the right. The dots represent molecules.
3. Using the ruler provided, the wavelength of the sound wave is measured to be _________.
4. Compared to the wavelengths of high-pitched sounds, the wavelengths of low-pitched sounds
are __________________.
long
short
5. Sound waves travel fastest in _________________.
solids
liquids
gases
... the same speed in each
6. The accepted value for the speed of sound in air is 331 m/s at 0ºC. The speed of sound in air
increases 0.6 m/s for each Celsius degree above zero. Compute the speed of sound at the
temperature of the room you are now in________________________________.
Refer to the following information for the next two questions.
7. Suppose you set your watch by the sound of the noon whistle from a factory 3 km away.
(a) Compared to the correct time, your watch
will be_______________.
(b) It will differ from the correct time by_____.
3 seconds
6 seconds
9 seconds
Refer to the following information for the next four questions.
8. Suppose a child's natural frequency of swinging is once each 4 seconds.
(a) For maximum amplitude the man should
push at a rate of once each ___________.
2 seconds
4 seconds
8 seconds
(b) If the man pushes in the same direction
twice as often, his pushes ___________.
will be effective
will not be effective
(c) This is
because__________________________.
the swing will be pushed twice as often in
the right direction
every other push will oppose the motion of
the swing
9. Based on this swing example, a 440 hztuning fork could NOT be forced into
vibration by a sound of _________.
220 hz
440 hz
880 hz
Refer to the following information for the next three questions.
10. Two notes with frequencies of 66 and 70 hertz are "sounded together."
(a) The resulting beat frequency is_________.
4 hertz
68 hertz
136 hertz
(b) At a pitch of ____________.
4 hertz
68 hertz
136 hertz
11. Beats are the result of the alternate
cancellation and reinforcement of two
sound waves of ___________.
the same
frequency
slightly different
frequencies
12. Why do flying insects produce a high-pitched buzzing sound?
13. A. An alarm clock is hung in a closed glass jar. When the alarm goes off, it can be heard. Why?
B. What would happen if the air were pumped out of the jar?
C. Why can you still hear the alarm clock?
14. Children often make a tin can---string—“telephone”. Explain the sound principles involved.
15. What happens to the energy when a sound “dies out”?
16. The speed of sound in air is given for still air. How would wind affect the propagation of sound?
What happens when you shout into the wind?
17. Sound travels faster in moist or humid air. Why is this?
(Hint: the major components of air are N2 and O2. In a volume of moist air, some of these
molecules are replaced by H2O molecules. Check out their masses, using the periodic table).
18. In a particular lecture demonstration, Mr. Lindsay breathes in helium (He) gas. When he talked
his voice had a high-pitched, “Donald Duck” sound. What causes this? (Hint: The vocal cavities
and wavelengths are still the same.)
19. How much faster does sound travel on a warm day when the temperature is 250C than on a cold
day, when the temperature is 00C?
20. How much faster does sound ravel on a warm day when the temperature is 250C than on a cold
day, when the temperature is 00C?
21. What happens to the wavelength of a sound wave if the frequency is doubled?
22. The distance between two condensations of a sound wave is 2 meters. Could this sound be
heard by a human ear if it were intense enough? (Take vs = 340 m/s and recall that fλ = v)
23. What are the wavelength limits of the audible range for human hearing? (use vs = 340 m/s)
24. While backpacking, you notice that there is a 4-second interval between seeing the lightning and
hearing the thunder from an approaching storm. Approximately how far away is the storm?
25. Why is an echo not as loud as the direct sound?
26. Why do sounds in an empty building or room sound “hollow”?
27. After a snowfall, it “sounds” particularly quiet. Why is this?
28. Singing in the shower is a popular pastime. Why does your voice sound fuller in the shower?
29. It is common to be able to hear music, particularly the bass part, through walls or ceilings (floors
if you are on top). What does this tell you about the natural frequency of the walls?
30. Is there a significant Doppler effect when a source moves at right angles to or by a stationary
observer at some distance? Explain.
31. If a sound source and an observer are both moving with the same velocity, is there a Doppler
effect? Explain.
32. Does a sonic boom occur only when a jet plane “breaks the sound barrier”? Explain.
33. How fast would a “jet” fish have to swim to create an “aquatic boom”?
34. Associate some Mach numbers with the adjectives subsonic, sonic, and supersonic.
35. A rocket travels at Mach 1.5 in the lower atmosphere, where the speed of sound is 330 m/s.
What is the speed of the rocket in m/s?
36. Do beats have anything to do with the beat of the music? Explain.
37. Is the effect the same when the sound level is increased from 10 to 20 dB as from 40 to 80 dB?
Explain.
38. When you hear a sound 1000 times the intensity of the faintest sound you can hear, what is the
intensity level of the sound in decibels?
39. Estimate the dB levels that might be heard from the sound sources shown below:
40. What is the effect when the base of the handle of a vibrating tuning fork is placed against a table
top? Is a similar effect used in musical instruments? Explain.
41. Suppose you break a string on a guitar and the only spare available is lighter than the broken
string. Using this string in a pinch, how would you compensate so the string produces the
proper tone?
42. Guitar keyboards have raised ridges or frets to show where the fingers should be placed, but
violins do not. Why do you suppose this is the case?
43. Give some examples of subjective sensory effects or differences for the senses other than
hearing.
44. What is the difference between a pure tone and a musical note?
45. REVIEW:
The diagram below shows a representation of two different waves.
Which of the following classifies wave X and wave Y?
A. Both waves are transverse.
B. Both waves are longitudinal.
C. Wave X is longitudinal and wave Y is transverse.
D. Wave X is transverse and wave Y is longitudinal.
46. REVIEW: A student is shaking one end of a small rug with a ball on top of it. The wave that is
produced travels through the rug and moves the ball upward, as shown in the diagram below.
Which type of wave is produced in the rug?
A. compression
B. electromagnetic
C. longitudinal
D. transverse
47. REVIEW: A student conducted two investigations using a toy car and microphones, as shown
below.
The toy car contained a buzzer. The microphones were used to record the frequency of sound. In
investigation 1, the buzzer frequency was measured while the toy car was at rest. In investigation 2, the
toy car was in motion and the observed frequency was measured in front of and behind the car. Which of
the following graphs represents the frequency recorded by each microphone?
48. REVIEW: The human ear is most sensitive to sound that has a frequency of about 4000 Hz.
Assume that the speed of sound in air is 340 m/s. What is the wavelength of a sound heard in
the air with this frequency?
A. 0.043 m
B. 0.085 m
C. 12 m
D. 340 m
49. REVIEW: Sound travels through air, steel, and water at different speeds. Which list is ordered
from the substance that sound will travel through the slowest to the substance that sound will
travel through the fastest?
A. air, water, steel
B. steel, air, water
C. water, air, steel
D. water, steel, air
50. REVIEW: Which of the following observed properties of a wave is changed by the Doppler
effect?
A. amplitude
51. REVIEW:
B. direction
C. frequency
D. speed
A. Wave X has half the amplitude of wave Y.
B. Wave X has twice the amplitude of wave Y.
C. Wave X has a lower frequency and longer wavelength than wave Y.
D. Wave X has a higher frequency and shorter wavelength than wave Y.