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Test Prep

# Test Prep

### Multiple Choice

#### 14.1Speed of Sound, Frequency, and Wavelength

1.

What properties does a loud, shrill whistle have?

1. high amplitude, high frequency
2. high amplitude, low frequency
3. low amplitude, high frequency
4. low amplitude, low frequency
2.
What is the speed of sound in fresh water at $20$ degrees Celsius?
1. $5960m/s$
2. $1540m/s$
3. $331m/s$
4. $1480m/s$
3.
A tuning fork oscillates at a frequency of $512Hz$, creating sound waves. How many waves will reach the eardrum of a person near that fork in $2$ seconds?
1. $512$
2. $128$
3. $256$
4. $1024$
4.
Why does the amplitude of a sound wave decrease with distance from its source?
1. The amplitude of a sound wave decreases with distance from its source, because the frequency of the sound wave decreases.
2. The amplitude of a sound wave decreases with distance from its source, because the speed of the sound wave decreases.
3. The amplitude of a sound wave decreases with distance from its source, because the wavelength of the sound wave increases.
4. The amplitude of a sound wave decreases with distance from its source, because the energy of the wave is spread over a larger and larger area.
5.
Does the elasticity of the medium affect the speed of sound? How?
1. No, there is no relationship that exists between the speed of sound and elasticity of the medium.
2. Yes. When particles are more easily compressed in a medium, sound does not travel as quickly through the medium.
3. Yes. When the particles in a medium do not compress much, sound does not travel as quickly through the medium.
4. No, the elasticity of a medium affects frequency and wavelength, not wave speed.

#### 14.2Sound Intensity and Sound Level

6.

Which of the following terms is a useful quantity to describe the loudness of a sound?

1. intensity
2. frequency
3. pitch
4. wavelength
7.

What is the unit of sound intensity level?

1. decibels
2. hertz
3. watts
8.
If a particular sound S1 is $5$ times more intense than another sound S2, then what is the difference in sound intensity levels in dB for these two sounds?
1. $5dB$
2. $6dB$
3. $7dB$
9.
By what minimum amount should frequencies vary for humans to be able to distinguish two separate sounds?
1. $100Hz$
2. $10Hz$
3. $5Hz$
4. $1Hz$
10.

Why is I0 chosen as the reference for sound intensity?

1. Because, it is the highest intensity of sound a person with normal hearing can perceive at a frequency of 100 Hz.
2. Because, it is the lowest intensity of sound a person with normal hearing can perceive at a frequency of 100 Hz.
3. Because, it is the highest intensity of sound a person with normal hearing can perceive at a frequency of 1000 Hz.
4. Because, it is the lowest intensity of sound a person with normal hearing can perceive at a frequency of 1000 Hz.

#### 14.3Doppler Effect and Sonic Booms

11.
In which of the following situations is the Doppler effect absent?
1. The source and the observer are moving towards each other.
2. The observer is moving toward the source.
3. The source is moving away from the observer.
4. Neither the source nor the observer is moving relative to one another.
12.
What does the occurrence of the sonic boom depend on?
1. speed of the source
2. frequency of source
3. amplitude of source
4. distance of observer from the source
13.
What is the observed frequency when the observer is moving away from the source at $125m/s$? The source frequency is $237Hz$ and the speed of sound is $325m/s$.
1. $303Hz$
2. $259Hz$
3. $201Hz$
4. $146Hz$
14.
How will your perceived frequency change if the source is moving towards you?
1. The frequency will become lower.
2. The frequency will become higher.

#### 14.4Sound Interference and Resonance

15.

Observation of which phenomenon can be considered proof that something is a wave?

1. interference
2. noise
3. reflection
4. conduction
16.

Which of the resonant frequencies has the greatest amplitude?

1. The first harmonic
2. The second harmonic
3. The first overtone
4. The second overtone
17.
What is the fundamental frequency of an open-pipe resonator?
1. $3v/2L$
2. $2v/L$
3. $v/L$
4. $v/2L$
18.
What is the beat frequency produced by the superposition of two waves with frequencies $300Hz$ and $340Hz$?
1. $640Hz$
2. $320Hz$
3. $20Hz$
4. $40Hz$

#### 14.1Speed of Sound, Frequency, and Wavelength

19.

What component of a longitudinal sound wave is analogous to a trough of a transverse wave?

1. compression
2. rarefaction
3. node
4. antinode
20.

What is the frequency of a sound wave as perceived by the human ear?

1. timbre
2. loudness
3. intensity
4. pitch
21.

What properties of a solid determine the speed of sound traveling through it?

1. mass and density
2. rigidity and density
3. volume and density
4. shape and rigidity
22.

Does the density of a medium affect the speed of sound?

1. No
2. Yes
23.

Does a bat make use of the properties of sound waves to locate its prey?

1. No
2. Yes
24.

Do the properties of a sound wave change when it travels from one medium to another?

1. No
2. Yes

#### 14.2Sound Intensity and Sound Level

25.
When a passing driver has his stereo turned up, you cannot even hear what the person next to you is saying. Why is this so?
1. The sound from the passing car’s stereo has a higher amplitude and hence higher intensity compared to the intensity of the sound coming from the person next to you. The higher intensity corresponds to greater loudness, so the first sound dominates the second.
2. The sound from the passing car’s stereo has a higher amplitude and hence lower intensity compared to the intensity of the sound coming from the person next to you. The lower intensity corresponds to greater loudness, so the first sound dominates the second.
3. The sound from the passing car’s stereo has a higher frequency and hence higher intensity compared to the intensity of the sound coming from the person next to you. The higher frequency corresponds to greater loudness so the first sound dominates the second.
4. The sound from the passing car’s stereo has a lower frequency and hence higher intensity compared to the intensity of the sound coming from the person next to you. The lower frequency corresponds to greater loudness, so the first sound dominates the second.
26.
For a constant area, what is the relationship between intensity of a sound wave and power?
1. The intensity is inversely proportional to the power transmitted by the wave, for a constant area.
2. The intensity is inversely proportional to the square of the power transmitted by the wave, for a constant area. $I=1P2$
3. The intensity is directly proportional to the square of the power transmitted by the wave, for a constant area. $I=P2$
4. The intensity is directly proportional to the power transmitted by the wave, for a constant area. $I=PA$
27.
What does $I$ stand for in the equation $β(dB)=10log10(II0)$? What is its unit?
1. Yes, $I$ is the sound intensity in watts per meter squared in the equation, $β(dB)=10log10(II0)$.
2. $I$ is the sound illuminance and its $SI$ unit is lumen per meter squared.
3. $I$ is the sound intensity and its $SI$ unit is watts per meter cubed.
4. $I$ is the sound intensity and its $SI$ unit is watts per meter squared.
28.
Why is the reference intensity $I0=10–12W/m2$?
1. The upper limit of human hearing is $100$ decibels, i.e. $β=100dB$. For $β=100dB$, $I0=10−12W/m2$.
2. The lower threshold of human hearing is $10$ decibels, i.e. $β=10dB$. For $β=10dB$, $I0=10−12W/m2$
3. The upper limit of human hearing is $10$ decibels, i.e. $β=10dB$. For $β=10dB$, $I0=10−12W/m2$
4. The lower threshold of human hearing is $0$ decibels, i.e., $β=0dB$. For $β=0dB$, $I0=10−12W/m2$
29.
Given that the sound intensity level of a particular wave is $82dB$, what will be the sound intensity for that wave?
1. $I=1.6×10−6W/m2$
2. $I=82×10−12W/m2$
3. $I=8.2×10−12W/m2$
4. $I=1.6×10−4W/m2$
30.
For a sound wave with intensity $1.58×10−4W/m2$, calculate the pressure amplitude given that the sound travels through air at $0∘C$.
1. $0.734Pa$
2. $3.67Pa$
3. $0.135Pa$
4. $0.367Pa$
31.

Which nerve carries auditory information to the brain?

1. buccal nerve
2. peroneal nerve
3. cochlear nerve
4. mandibular nerve
32.
Why do some smaller instruments, such as piccolos, produce higher-pitched sounds than larger instruments, such as tubas?
1. Smaller instruments produce sounds with shorter wavelengths, and thus higher frequencies.
2. Smaller instruments produce longer wavelength, and thus higher amplitude, sounds.
3. Smaller instruments produce lower amplitude, and thus longer wavelength sounds.
4. Smaller instruments produce higher amplitude, and thus lower frequency, sounds.

#### 14.3Doppler Effect and Sonic Booms

33.
How will your perceived frequency change if you move away from a stationary source of sound?
1. The frequency will become lower.
2. The frequency will be doubled.
3. The frequency will be tripled.
4. The frequency will become higher.
34.

True or false—The Doppler effect also occurs with waves other than sound waves.

1. False
2. True
35.
A source of sound is moving towards you. How will what you hear change if the speed of the source increases?
1. The sound will become more high-pitched.
2. The sound will become more low-pitched.
3. The pitch of the sound will not change.
36.
Do sonic booms continue to be created when an object is traveling at supersonic speeds?
1. No, a sonic boom is created only when the source exceeds the speed of sound.
2. Yes, sonic booms continue to be created when an object is traveling at supersonic speeds.
37.
Suppose you are driving at a speed of $20.0m/s$ and you hear the sound of a bell at a frequency of $400.0Hz$. What is the actual frequency of the bell if the speed of sound is $335m/s$?
1. $fs=401Hz orfs=315Hz$
2. $fs=385Hz orfs=419Hz$
3. $fs=415Hz orfs=366Hz$
4. $fs=425Hzorfs=377Hz$
38.
What is the frequency of a stationary sound source if you hear it at $1200.0Hz$ while moving towards it at a speed of $50.0m/s$? (Assume speed of sound to be $331m/s$.)
1. $1,410Hz$
2. $1,380Hz$
3. $1,020Hz$
4. $1,042Hz$

#### 14.4Sound Interference and Resonance

39.
What is the actual frequency of the wave produced as a result of superposition of two waves?
1. It is the average of the frequencies of the two original waves that were superimposed.
2. It is the difference between the frequencies of the two original waves that were superimposed.
3. It is the product of the frequencies of the two original waves that were superimposed.
4. It is the sum of the frequencies of the two original waves that were superimposed.
40.
Can beats be produced through a phenomenon different from resonance? How?
1. No, beats can be produced only by resonance.
2. Yes, beats can be produced by superimposition of any two waves having slightly different frequencies.
41.
How is human speech produced?
1. Human speech is produced by shaping the cavity formed by the throat and mouth, the vibration of vocal cords, and using the tongue to adjust the fundamental frequency frequency and combination of overtones.
2. Human speech is produced by shaping the cavity formed by the throat and mouth into a closed pipe and using tongue to adjust the fundamental and combination of overtones.
3. Human speech is produced only by the vibrations of the tongue.
4. Human speech is produced by elongating the vocal cords.
42.
What is the possible number of nodes and antinodes along one full wavelength of a standing wave?
1. $2$ nodes and $3$ antinodes or $2$ antinodes and $3$ nodes.
2. $2$ nodes and $2$ antinodes or $3$ antinodes and $3$ nodes.
3. $3$ nodes and $3$ antinodes or $2$ antinodes and $2$ nodes.
4. $6$ nodes and $4$ antinodes or $6$ antinodes and $4$ nodes.
43.
In a pipe resonator, which frequency will be the least intense of those given below?
1. second overtone frequency
2. first overtone frequency
3. fundamental frequency
4. third overtone frequency
44.
A flute is an open-pipe resonator. If a flute is $60cm$ long, what is the longest wavelength it can produce?
1. $240cm$
2. $180cm$
3. $60cm$
4. $120cm$
45.
What is the frequency of the second overtone of a closed-pipe resonator with a length of $22.0cm$? (Assume the speed of sound is $331m/s$.)
1. $7,520Hz$
2. $1,510Hz$
3. $376Hz$
4. $1,880Hz$
46.
An open-pipe resonator has a fundamental frequency of $220Hz$ when the speed of sound is $331m/s$. What will its fundamental frequency be when the speed of sound is $350m/s$?
1. $690Hz$
2. $470Hz$
3. $110Hz$
4. $230Hz$

### Extended Response

#### 14.1Speed of Sound, Frequency, and Wavelength

47.
How is a human able to hear sounds?
1. Sound waves cause the eardrum to vibrate. A complicated mechanism converts the vibrations to nerve impulses, which are perceived by the person as sound.
2. Sound waves cause the ear canal to vibrate. A complicated mechanism converts the vibrations to nerve impulses, which are perceived by the person as sound.
3. Sound waves transfer electrical impulses to the eardrum. A complicated mechanism converts the electrical impulses to sound.
4. Sound waves transfer mechanical vibrations to the ear canal, and the eardrum converts them to electrical impulses.
48.
Why does sound travel faster in iron than in air even though iron is denser than air?
1. The density of iron is greater than that of air. However, the rigidity of iron is much greater than that of air. Hence, sound travels faster in it.
2. The density of iron is greater than that of air. However, the rigidity of iron is much less than that of air. Hence, sound travels faster in it.
3. The density of iron is greater than that of air. However, the rigidity of iron is equal to that of air. Hence, sound travels faster in it.
4. The mass of iron is much less than that of air and the rigidity of iron is much greater than that of air. Hence, sound travels faster in it.
49.

Is the speed of sound dependent on its frequency?

1. No
2. Yes

#### 14.2Sound Intensity and Sound Level

50.
Why is the sound from a tire burst louder than that from a finger snap?
1. The sound from the tire burst has higher pressure amplitudes, hence it can exert smaller force on the eardrum.
2. The sound from the tire burst has lower pressure amplitudes, hence it can exert smaller force on the eardrum.
3. The sound from the tire burst has lower pressure amplitudes, hence it can exert larger force on the ear drum.
4. The sound from the tire burst has higher pressure amplitudes, hence it can exert larger force on the eardrum.
51.
Sound A is $1000$ times more intense than Sound B. What will be the difference in decibels in their sound intensity levels?
1. $5dB$
2. $10dB$
3. $3dB$
4. $30dB$
52.
The ratio of the pressure amplitudes of two sound waves traveling through water at $0∘C$ is $4.0$. What will be the difference in their sound intensity levels in dB?
1. $1.2dB$
2. $6.0dB$
3. $0.60dB$
4. $12dB$
53.
Which of the following most closely models how sound is produced by the vocal cords?
1. A person plucks a string.
2. A person blows over the mouth of a half-filled glass bottle.
3. A person strikes a hammer against a hard surface.
4. A person blows through a small slit in a wide, stretched rubber band.

#### 14.3Doppler Effect and Sonic Booms

54.

True or false—The Doppler effect occurs only when the sound source is moving.

1. False
2. True
55.

True or false—The observed frequency becomes infinite when the source is moving at the speed of sound.

1. False
2. True
56.
You are driving alongside a train. You hear its horn at a pitch that is lower than the actual frequency. What should you do to match the speed of the train? Why?
1. In order to match the speed of the train, one would need to increase or decrease the speed of his/her car because a lower pitch means that either the train (the source) is moving away or that you (the observer) are moving away.
2. In order to match the speed of the train, one would need to drive at a constant speed because a lower pitch means that the train and the car are at the same speed.

#### 14.4Sound Interference and Resonance

57.
How are the beat frequency and the regular frequency of a wave resulting from superposition of two waves different?
1. Beat frequency is the sum of two frequencies and regular frequency is the difference between frequencies of two original waves.
2. Beat frequency is the difference between the constituent frequencies, but the regular frequency is the average of the frequencies of the two original waves.
3. Beat frequency is the sum of two frequencies and regular frequency is the average of frequencies of two original waves.
4. Beat frequency is the average of frequencies of two original waves and regular frequency is the sum of two original frequencies.
58.
In the tuning fork and tube experiment, if resonance is formed for $L=λ/4$, where $L$ is the length of the tube and $λ$ is the wavelength of the sound wave, can resonance also be formed for a wavelength $λ=4L/9$? Why?
1. The frequency formed is a harmonic and first overtone so resonance will occur.
2. The frequency formed is a harmonic and second overtone so resonance will occur.
3. The frequency formed is a harmonic and third overtone so resonance will occur.
4. The frequency formed is a harmonic and fourth overtone so resonance will occur.
59.

True or false—An open-pipe resonator has more overtones than a closed-pipe resonator.

1. False
2. True
60.
A flute has finger holes for changing the length of the resonating air column, and therefore, the frequency of the note played. How far apart are two holes that, when closed, play two frequencies that are $300.0Hz$ apart, if the first hole is $20.0cm$ away from the mouthpiece of the flute?
1. $0.31m$
2. $0.24m$
3. $0.04m$
4. $0.11m$