Chapter 21 Study Questions Name: _________________________ Class: ________________
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____
____
____
____
____
____
____
____
____
____
____
____
____
____
1. If a fire engine is traveling toward you, the Doppler effect will cause the siren to sound
a. higher.
c. louder.
b. lower.
d. softer.
2. The wave interaction most important for echolocation is
a. reflection.
c. diffraction.
b. interference.
d. resonance.
3. If two sound waves interfere constructively, you will hear
a. a high-pitched sound.
c. a louder sound.
b. a softer sound.
d. no change in sound.
4. You will hear a sonic boom when
a. an object breaks the sound barrier.
c. a shock wave reaches your ears.
b. an object travels at supersonic speeds.
d. the speed of sound is 290 m/s.
5. Instruments that produce sound when struck belong to which family?
a. strings
c. percussion
b. winds
d. None of the above
6. Resonance can occur when an object vibrates at another object’s
a. resonant frequency.
c. second overtone frequency.
b. fundamental frequency.
d. All of the above
7. The amount of diffraction that a sound wave undergoes depends on
a. the frequency of the wave.
c. the size of the barrier.
b. the amplitude of the wave.
d. Both (a) and (c)
8. A technological device that can be used to “see” sound waves is a(n)
a. oscilloscope.
c. transducer.
b. sonar.
d. amplifier.
9. Which statement about sound is true?
a. Air particles travel with sound waves.
b. Sound waves can travel through a vacuum.
c. Sound waves exist only if someone hears them.
d. Air particles vibrate along the path of a sound wave.
10. Sound waves are best reflected off ____ surfaces.
a. bumpy, soft
c. smooth, hard
b. smooth, soft
d. bumpy, hard
11. The speed of a sound depends on
a. its source.
c. the number of waves per second.
b. the force of its compressions.
d. the medium through which it travels.
12. For a sound wave to produce an echo, it must
a. diffract around a small barrier.
c. have an ultrasonic frequency.
b. reflect off the surface of an object.
d. have a very long wavelength.
13. The complete back-and-forth motion of an object is called a
a. compression.
c. vibration.
b. rarefaction.
d. wave.
14. As air particles are pushed closer together, they create a region of higher density and pressure called a
____ 15.
____ 16.
____ 17.
____ 18.
____ 19.
____ 20.
____ 21.
____ 22.
____ 23.
____ 24.
____ 25.
a. compression.
c. rarefaction.
b. vibration.
d. wave.
A ____ is created when air particles become less crowded and create a region of lower density and pressure.
a. wave
c. vibration
b. rarefaction
d. compression
Sound is transmitted through air away from a stereo-speaker cone because
a. the vibrating cone creates visible waves in air.
b. the cone always vibrates at a faster rate than the air particles.
c. compressions and rarefactions travel away from the cone.
d. None of the above
As the speaker cone in a stereo speaker moves forward, it pushes air particles
a. farther away from each other, creating a compression.
b. closer together, creating a compression.
c. farther away from each other, creating a rarefaction.
d. closer together, creating a rarefaction.
As the speaker cone in a stereo speaker moves backward, the air particles close to the cone become
a. more crowded, creating a compression.
b. less crowded, creating a compression.
c. more crowded, creating a rarefaction.
d. less crowded, creating a rarefaction.
A disturbance that transmits energy through matter or space is called a
a. compression.
c. rarefaction.
b. vibration.
d. wave.
Sound travels as a(n)
a. longitudinal wave.
c. electromagnetic wave.
b. transverse wave.
d. All of the above
Sound is transmitted through
a. a vacuum.
b. the vibrations and collisions of particles of matter.
c. the movement of electromagnetic waves.
d. the interference of transverse waves.
Which of the following does NOT happen to air particles as a sound wave travels through air?
a. They vibrate in place.
c. They form compressions.
b. They travel with the sound wave.
d. They form rarefactions.
Which of the following would produce a sound that does NOT have a random mix of frequencies?
a. a trumpet
c. a barking dog
b. a car engine
d. a radio tuned to a talk show
When you speak, your vocal cords
a. create compressions.
c. vibrate.
b. create rarefactions.
d. All of the above
If an astronaut popped a balloon on the moon, would his partner hear it?
a. Yes, the air expanding out of the balloon as it popped will transmit the sound waves to his
partner.
b. No, the moon has no atmosphere so there is no medium through which the sound waves
can be transmitted.
c. No, although the sound waves will travel to his partner, the sound waves would not be
transmitted through his partner's helmet.
d. Yes, the sound waves will first be transmitted through the astronaut's body, then through
the ground, and finally through his partner's body.
____ 26. Changing the ____ of air affects the speed of sound through the air.
a. mass
c. chemical composition
b. temperature
d. None of the above
Speed of Sound in
Different Media at 20°C
Medium
Speed
Air
343
Helium
1,005
Water
1,482
Sea Water
1,522
Wood (oak)
3,850
Glass
4,540
Steel
5,200
____ 27. How far does sound travel in 5 seconds through glass at 20ºC?
a. 908 m
c. 4,545 m
b. 1,715 m
d. 22,700 m
____ 28. How long does it take for sound to travel 3,044 m through sea water at 20ºC?
a. 0.5 s
c. 3 s
b. 2 s
d. 9 s
____ 29. How far does sound travel in 2.5 seconds through oak wood at 20ºC?
a. 154 m
c. 3,875 m
b. 3,825 m
d. 9,625 m
____ 30. The speed of sound in air ____ as the temperature decreases.
a. decreases
c. stays the same
b. increases
d. triples
____ 31. A thick tuning fork vibrates at a ____ frequency and creates a sound with a ____ pitch.
a. high; high
c. high; low
b. low; low
d. low; high
____ 32. Sounds with frequencies that are lower than 20 Hz are called
a. infrasonic.
c. ultrasonic.
b. subsonic.
d. supersonic.
____ 33. Sounds with very high frequencies that are used to break down kidney stones are called
a. infrasonic.
c. ultrasonic.
b. subsonic.
d. supersonic.
____ 34. ____ waves are used to break down kidney stones, clean jewelry, and examine internal organs.
a. Subsonic
c. Ultrasonic
b. Infrasonic
d. Supersonic
____ 35. The frequency of a car horn appears to change as a car passes because
a. of the Doppler effect.
c. frequency increases with a car's speed.
b. sound travels faster in air than in glass.
d. frequency decreases with a car's speed.
____ 36. As a car with a honking horn approaches a listener, sound waves from the horn are
a. closer together and have a higher frequency.
b. farther apart and have a higher frequency.
c. closer together and have a lower frequency.
d. farther apart and have a lower frequency.
____ 37. As a car with a honking horn moves away from a listener, sound waves from the horn are
a. closer together and have a higher frequency.
____ 38.
____ 39.
____ 40.
____ 41.
____ 42.
____ 43.
____ 44.
____ 45.
____ 46.
____ 47.
____ 48.
____ 49.
b. farther apart and have a higher frequency.
c. closer together and have a lower frequency.
d. farther apart and have a lower frequency.
The Doppler effect is perceived when a
a. listener in front of a moving car hears a higher pitch than a listener behind the car.
b. listener in front of a moving car hears a lower pitch than a listener behind the car.
c. listener behind a moving car hears a higher pitch than a listener in front of the car.
d. Both (a) and (b)
The ____ of a wave is the maximum distance the particles in a wave vibrate from their rest positions.
a. rarefaction
c. amplitude
b. compression
d. frequency
As the amplitude of a wave increases,
a. the softer a sound becomes.
c. the higher the frequency becomes.
b. the louder a sound becomes.
d. Both (b) and (c)
A wave is ____ when it strikes a barrier and bounces back.
a. compressed
c. reflected
b. diffracted
d. resonated
Fishermen can determine the location of fish by using electronic echolocation technology called
a. sonar.
c. ultrasound.
b. radar.
d. infrasound.
____ is used to check development of an unborn baby inside a mother's body.
a. Infrasonography
c. Multisonography
b. Ultrasonography
d. Echolocography
In which of the following places would you most likely hear echoes?
a. in a forest
c. in a recording studio
b. in a gymnasium
d. in an airplane
____ is the result of two or more sound waves overlapping.
a. Reflection
c. Diffraction
b. Interference
d. Resonance
Constructive interference occurs when
a. the rarefactions of one wave overlap the rarefactions of another wave.
b. the compressions of one wave overlap the rarefactions of another wave.
c. the compressions of one wave overlap the compressions of another wave.
d. Both (a) and (c)
Destructive interference occurs when
a. the rarefactions of one wave overlap the rarefactions of another wave.
b. the compressions of one wave overlap the rarefactions of another wave.
c. the compressions of one wave overlap the compressions of another wave.
d. None of the above
When destructive interference occurs, a sound will be
a. louder because the amplitude is increased.
b. louder because the amplitude is decreased.
c. softer because the amplitude is increased.
d. softer because the amplitude is decreased.
When constructive interference occurs, a sound will be
a. louder because the amplitude is increased.
b. louder because the amplitude is decreased.
c. softer because the amplitude is increased.
d. softer because the amplitude is decreased.
____ 50. A ____ wave is a result of interference in which portions of the wave are at the rest position and other
portions have a large amplitude.
a. reflected
c. standing
b. refracted
d. transverse
____ 51. A plucked guitar string creates several
a. diffraction waves.
c. refracted waves.
b. standing waves.
d. reflected waves.
____ 52. ____ occurs when an object vibrating at or near a certain frequency causes a second object to vibrate.
a. Resonance
c. Echolocation
b. Diffraction
d. Reflection
____ 53. ____ is the bending of waves around barriers or through openings.
a. Resonance
c. Echolocation
b. Diffraction
d. Reflection
____ 54. The lowest resonant frequency of a standing wave is called the
a. fundamental.
c. node.
b. third overtone.
d. amplitude.
____ 55. Resonant frequencies higher than the lowest resonant frequency of a standing wave are called
a. nodes.
c. overtones.
b. fundamentals.
d. amplitudes.
____ 56. Some dental hygienists use ultrasound to clean the tartar from patients' teeth because the frequency of the
ultrasound wave matches the frequency of the chemical bonds in the tartar. The tartar shatters because of
a. reflection.
c. resonance.
b. refraction.
d. diffraction.
____ 57. If you blow across the mouth of an empty glass bottle, you hear the lowest resonant frequency which is called
the
a. fundamental.
c. second overtone.
b. first overtone.
d. third overtone.
Below are diagrams of sound waves moving from one room into another through a door. Each sound wave
moves from left to right. Study the diagrams and answer the questions that follow.
____ 58. The diagrams illustrate the bending of sound waves through openings, which is called
a. refraction.
c. diffraction.
b. reflection.
d. interference.
____ 59. Which diagram illustrates high-frequency sound waves moving from one room into another through a door?
a. A
c. Both (a) and (b)
b. B
d. Neither (a) nor (b)
____ 60. Which diagram illustrates low-frequency sound waves moving from one room into another through a door?
a. A
c. Both (a) and (b)
b. B
d. Neither (a) nor (b)
____ 61. Diagram A illustrates that ____ can be hard to hear when you are in the next room.
____ 62.
____ 63.
____ 64.
____ 65.
____ 66.
a. fundamental frequencies
c. high pitches
b. resonant frequencies
d. low pitches
Diagram B best illustrates that ____ when you are in the next room.
a. high pitches are easier to hear
c. low pitches are harder to hear
b. high pitches are harder to hear
d. low pitches are easier to hear
From the diagrams above it can be inferred that when you speak to a person in another room, it is best to
speak with a
a. higher pitch.
c. lower pitch.
b. higher frequency.
d. Both (a) and (b)
Thunder consists of
a. only low-frequency sound waves.
b. only high-frequency sound waves.
c. both high- and low-frequency sound waves.
d. neither high- nor low-frequency sound waves.
The rumbling sound of thunder is heard when lightning strikes far away because
a. thunder has only high frequencies.
b. thunder has only low frequencies.
c. only high-frequency waves can diffract around trees, buildings, hills, and other barriers.
d. only low-frequency waves can diffract around trees, buildings, hills, and other barriers.
Sound that includes a random mix of pitches is called
a. sound quality.
c. diffraction.
b. noise.
d. music.
You attend a July 4th firework celebration in your town. You find a seat that has a good view of the fireworks
display, where you are 700 m away from the point the fireworks are being set off.
____ 67. During the show, you notice that you see the lights of the fireworks before you hear the explosive sounds.
This happens because the speed of
a. light is faster than the speed of sound in air.
b. sound is faster than the speed of light in air.
c. the speed of light and sound are the same in air.
d. None of the above
____ 68. If three seconds pass from the time you see an explosion to the time you hear the boom, the speed of sound is
a. 330 m/s.
c. 700 m/s.
b. 350 m/s.
d. 1400 m/s.
____ 69. It takes three seconds for the sound of an explosion to reach you. If the speed of sound in air is 343 m/s at
20°C, then the air temperature during the fireworks display is
a. 20°C.
b. greater than 20°C.
c. less than 20°C.
d. Unimportant in the determination of the speed of sound in air.
____ 70. Suppose you live 1 km away from a high school. Every morning, you hear the high school marching band
practice in the football stadium. The reason you hear the percussion instruments and tubas is because
a. of sound quality.
b. tubas and percussion instruments have no pitch.
c. high frequency waves do not diffract as much as low frequency waves.
d. low frequency waves do not diffract as much as high frequency waves.
____ 71. Suppose you live three blocks from your town's clock tower. You are LEAST likely to hear the clock toll its
bells when the weather is
a. cloudy.
b. foggy.
c. snowy.
d. sunny.
Short Answer
72. Examine the chart below, and answer the question that follows.
Sound
a soft whisper
leaves rustling
normal conversation
automobile accelerating
motorcycle engine
rock concert
jet plane taking off
Decibel level
20
30
60
70
110
120
140
What is a reasonable estimate of the range of decibel levels the human voice can produce?
73. Look at the oscilloscope screen below. Do you think the sound represented by the wave on the screen was
noise or music? Explain your answer.
74. How far does sound travel in 4 seconds through water at 20ºC and glass at 20ºC? Refer to the chart below for
the speed of sound in different media.
Speed of Sound in
Different Media at 20°C
Medium
Speed
Air
343
Helium
1,005
Water
1,482
Sea Water
1,522
Wood (oak)
3,850
Glass
4,540
Steel
5,200
Use the oscilloscope screens below to answer the following questions.
75. Which sound is probably noise?
76. Which represents the softest sound?
77. Which represents the sound with the lowest pitch?
78. Which two sounds were produced by the same instrument?