b.
d.
42. The 3rd harmonic of a complex tone has a frequency of 1,200 Hz. The frequency of the tone
is
a.
200 Hz
c.
600 Hz
b.
400 Hz
d.
none of the above
43. A sound level of 80 dB has ___________ the amplitude of a 60 dB sound.
a.
ten times
c.
one tenth
b.
twenty times
d.
twice
44. A zero decibel sound level
a.
has zero amplitude
c.
is just at the threshold of hearing.
b.
is nonsense
d.
none of the above
45. Combining two sounds of equal intensity will give a sound level ___________ than the
sound level due to just one of them.
a.
twice as loud
c.
10 dB higher
b.
3 dB higher
d.
2 dB higher
46. If one lawn mower causes an 80 dB sound level at a point nearby, four lawnmowers
together would cause a sound level of ____________ at that point.
a.
92 dB
c.
86 dB
b.
84 dB
d.
none of the above
47. If you move twice as far away from a lawn mower running in an open field, the amplitude
of the sound you hear will be ___________ what it was before.
a.
the same as
b.
twice
c.
half
d.
four times
e.
one fourth
48. A sound with ten times the amplitude of another sound is judged to be
a.
twice as loud
c.
10 dB higher in sound level
b.
ten times as loud
d.
20 dB higher in sound level
49. Harmonics
a.
are components of a complex waveform
b.
have frequencies that are integer multiples of the frequency of the complex
waveform
c.
are pure tones
d.
have sinusoidal waveforms
e.
all of the above
50. In the upper atmosphere at altitudes where commercial airlines travel, we find extremely
cold temperatures. What is the speed of sound (in metric units) for a temperature of -49.0
oC?
a.
984.9 m/s
c.
344.7 m/s
b.
300.8 m/s
d.
140.7 m/s
51. What frequency of sound traveling in air at 40 oC has a wavelength of 0.50 m?
a.
20 Hz
c.
502.9 Hz
b.
344.7 Hz
d.
711.2 Hz
52. You are on an island where a huge explosion at a distance of 500 miles away can be heard.
How long (in seconds) does it take the sound to travel to your location? Assume the
temperature of the air is 20 oC.
a.
1.4 s
c.
2340.1 s
b.
5.6 s
d.
8955.4 s
53. You are on a boat in a fog and know there are cliffs ahead of you somewhere, but you
cannot see them. You use your fog horn to send out a blast of sound (assume the
temperature of the air is 20 oC) and the time it takes for the sound to return to you is 20.0 s.
How far away are the cliffs (in metric units)? Hint: Be careful and think about the physics of
the problem. You may want to make a sketch of the situation to help you determine the
answer.
a.
1798 m
c.
3596 m
b.
3444 m
d.
7192 m
54. Sound waves propagate in
a.
one dimension
c.
three dimensions
b.
two dimensions
d.
four dimensions
MULTIPLE RESPONSE
1. An example of a transverse wave is a
a.
sound wave in air
b.
wave on a rope
c.
water wave
d.
sound wave in a metal bar
e.
none of the above
2. An example of a longitudinal wave is a
a.
sound wave in air
b.
wave on a rope
c.
water wave
d.
sound wave in a metal bar
e.
none of the above
3. In a plane wave, the wavefronts are
a.
circular
b.
flat
c.
parallel
d.
perpendicular to the direction of propagation
4. The wave with the largest wavelength is wave
a.
I
b.
II
c.
III
d.
IV
e.
all of the above
5. The wave with the largest amplitude is
a.
I
b.
II
c.
III
d.
IV
e.
all of the above
6. The wave with the largest frequency is
a.
I
b.
II
c.
III
d.
IV
e.
all of the above
7. In order for two waves to interfere completely destructively, they must
a.
have the same amplitude
b.
be exactly out of phase
c.
one wave’s peak must align with the other’s valley
d.
be transverse waves
e.
all of the above
8. You put one ear on a steel railroad track while your friend a distance of 400 m away taps on
the rail with a stone. You will hear the sound through the steel rail in _________ and
through the air where the speed of sound is 344 m/s in _______.
a.
0.08 s
c.
1.2 s
b.
0.5 s
d.
2.4 s
1. The number of cycles of a wave passing a point per unit time is the wave’s __________.
2. A complex tone can be produced by combining two or more __________.
3. The distance between two successive ‘like’ points on a wave is the wave’s __________.
4. The maximum displacement of points on a wave from the equilibrium position is the wave’s
__________.
5. A _________ wave is one with its oscillations perpendicular to the direction of propagation.
6. The wavelength of a wave multiplied by the frequency of the wave is the wave’s
__________.
7. Two examples of a longitudinal wave are __________ and __________.
8. Two examples of a transverse wave are __________ and __________.
NARREND
9. The waves with the largest wavelength are waves __________ and ___________.
10. The waves with the largest amplitude are _________ and _________.
11. The waves with the largest frequency are __________ and _________.
12. The wave with the greatest speed is __________.
13. A wave moves in a rope with a certain wavelength. A second wave is made to move in the
same rope with twice the wavelength of the first wave. The frequency of the second wave is
_________ times the frequency of the first wave.
14. Increasing the speed of waves on a guitar string increases the _________ of the sound it
produces.
15. You shout at a cliff, and hear your echo in 2 seconds. If the speed of sound in the air is 340
m/s, the distance of the cliff from you is __________.
16. You can hear sound through an open window from sources that are not in your line of sight
because of __________.
17. Two speakers in a stereo emit identical pure tones. As you move around in front of the
speakers, you hear the sound alternating between loud and zero. This occurs because of
__________.
18. When two identical waves undergo _______________ interference, the net amplitude is
zero.
19. As you move farther away from a source emitting a pure tone, the __________ of the sound
you hear decreases.
20. In ultrasound the __________ of the sound is much greater than in normal sound.
21. Two uses of ultrasound are __________ and __________.
22. The wavelength of ultrasound at 1 million Hz in air where the speed of sound is 340 m/s is
__________.
23. The only way to make sound travel faster in air is to change the air’s ____________.
24. A sound level of 80 dB has __________ times the amplitude of a 60 dB sound.
25. Combining two sounds of equal intensity will give a sound level __________ higher than
the sound level due to just one of them.
26. As you increase in altitude in the atmosphere, the speed of sound _________.
27. If the speed of a continuous wave is constant, as you increase the frequency of the wave, the
wave must have a proportionally _________ wavelength
MATCHING
Match each item with the correct statement below.
a.
amplitude
i.
ray
b.
constructive interference
j.
reflection
c.
destructive interference
k.
reverberation
d.
diffraction
l.
sound level
e.
Doppler effect
m.
transverse
f.
frequency
n.
ultrasound
g.
longitudinal
o.
waveform
h.
pitch
p.
wavelength
1. line used to show the path of a wave
2. occurs when two waves arrive in phase
3. occurs when sound passes through an open window
4. sound waves used to form images of internal organs
5. the maximum displacement of points on a wave
6. the number of cycles of a wave passing a point per unit time
7. measured in decibels
8. the distance between two successive ‘like’ points on a wave
9. sound in air is an example of this type of wave
10. affects the frequency of the sound from a moving sound source
11. multiple, random reflection of sound inside a room
12. when two wave are “out of phase” the result is
PROBLEM
1. What is the speed of sound in the air inside a furnace where the temperature is 500 degrees
Celsius (773 Kelvin)?
2. Water ripples are produced by making a cork oscillate up and down at a frequency of 5 Hz.
The peaks of the ripples are 0.03 meters apart. What is the speed of the water ripples?
3. A test tone used on a radio has a frequency of 1,000 Hz. What is the wavelength of this
sound in air at normal room temperature? (The speed of sound is 344 meters per second.)
4. A huge explosion is heard 20 miles away. How long does it take the sound to travel that far?
(20 miles = 32,000 meters)
5. The fourth harmonic of a complex tone has a frequency of 600 Hz. What is the frequency of
the tone?
6. If one lawn mower causes an 80 dB sound level at a nearby point, what sound level at that
point would four lawnmowers together cause?
7. In the upper atmosphere at altitudes where commercial airlines travel, we find extremely
cold temperatures. What is the speed of sound (in metric units) for a temperature of -53.0
oC?