Deck 14: Sound

Question 1

Tripling the power output from a speaker emitting a single frequency will result in what increase in loudness?

A)0.33 dB
B)3.0 dB
C)4.8 dB
D)9.0 dB

Answer 1

4.8 dB

Question 2

Comparing the speed of sound in liquids, gases, and solids, the speed of sound is usually lowest in ____ and highest in ____.

A)solids, liquids
B)gases, liquids
C)liquids, solids
D)gases, solids

Answer 2

gases, solids

Question 3

How far away is a lightning strike if you hear the thunderclap 3.00 s after you see the lightning bolt strike? (v_sound = 340 m/s, v_light = 3 * 10⁸ m/s)

A)113 m
B)340 m
C)680 m
D)1 020 m

Answer 3

1 020 m

Question 4

A sound wave coming from a tuba has a wavelength of 1.50 m and travels to your ears at a speed of 345 m/s.What is the frequency of the sound you hear?

A)517 Hz
B)1/517 Hz
C)230 Hz
D)1/230 Hz

Question 5

A sound wave in air has a frequency of 500 Hz and a wavelength of 0.68 m.What is the air temperature?

A)-18 $\degree$ C
B)0 $\degree$ C
C)15 $\degree$ C
D)27 $\degree$ C

Question 6

When a sine wave is used to represent a sound wave, the crest corresponds to:

A)rarefaction.
B)condensation.
C)point where molecules vibrate at a right angle to the direction of wave travel.
D)region of low elasticity.

Question 7

Which of the following ranges corresponds to the longest wavelengths?

A)infrasonic
B)audible
C)ultrasonic
D)all have the same wavelengths

Question 8

Consider a vibrating string that makes a sound wave that moves through the air.As the guitar string moves up and down, the air molecules that are a certain horizontal distance from the string will move:

A)up and down.
B)toward and away from the guitar string.
C)back and forth along the direction of the length of the string.
D)in circles around the guitar string.

Question 9

A series of ocean waves, 5.0 m between crests, move past at 2.0 waves/s.Find their speed.

A)2.5 m/s
B)5.0 m/s
C)8.0 m/s
D)10 m/s

Question 10

The speed of sound in air is a function of which one of the following?

A)wavelength
B)frequency
C)temperature
D)amplitude

Question 11

When a sound wave moves through a medium such as air, the motion of the molecules of the medium is in what direction (with respect to the motion of the sound wave)?

A)perpendicular
B)parallel
C)anti-parallel (in opposite direction)
D)Both choices b and c are valid.

Question 12

If the intensity of a sound is increased by a factor of 100, how is the decibel level changed? The new decibel level will be:

A)two units greater.
B)double the old one.
C)ten times greater.
D)twenty units greater.

Question 13

If one-third of the members of a symphony orchestra are absent because of head colds, thus reducing the overall intensity of sound by 33%, what will be the reduction in the decibel level?

A)30 dB
B)3 dB
C)48 dB
D)1.7 dB

Question 14

The speed of sound at 0 $\degree$ C is 331 m/s.What is the speed of sound at 25 $\degree$ C? (0 $\degree$ C = 273 K)

A)346 m/s
B)356 m/s
C)343 m/s
D)350 m/s

Question 15

Assuming that the wave speed varies little when sound waves are traveling though a material that suddenly changes density by 10%, what percentage of the incident wave intensity is reflected?

A)< 1%
B)5%
C)10%
D)20%

Question 16

The frequency separating audible waves and ultrasonic waves is considered to be 20 kHz.What wavelength in air at room temperature is associated with this frequency? (Assume the speed of sound to be 340 m/s.)

A)1.7 cm
B)5.2 cm
C)34 cm
D)55 cm

Question 17

The density of a certain metal solid is 7.2 * 10³ kg/m³, and its Young's modulus is 10 * 10¹⁰ N/m².What is the speed of sound in this metal?

A)1.4 * 10⁷ m/s
B)5 900 m/s
C)3 700 m/s
D)3 000 m/s

Question 18

What is the intensity level of a sound with intensity of 5.0 * 10^-10 W/m²? (I₀ = 10^-12 W/m²)

A)74 dB
B)54 dB
C)2.7 dB
D)27 dB

Question 19

If I₀ = 10^-12 W/m² is the threshold of hearing, a sound with intensity I₁ = 10^-11 W/m² will give a certain decibel level.Suppose a new sound has an intensity I₂ = I₁²/I₀.What is the new decibel level?

A)2.0
B)20
C)100
D)it will square the decibel level

Question 20

What is the intensity of a sound with a measured intensity level of 84 dB? (I₀ = 10^-12 W/m²)

A)8.4 * 10^-3 W/m²
B)2.5 * 10^-4 W/m²
C)1.2 * 10^-5 W/m²
D)7.4 * 10^-4 W/m²

Question 21

By what amount does the sound intensity decrease when the distance to the source doubles?

A)1.4 dB
B)2.0 dB
C)4.0 dB
D)6.0 dB

Question 22

If the distance between a point sound source and a dB detector is increased by a factor of 4, what will be the reduction in intensity level?

A)16 dB
B)12 dB
C)4 dB
D)0.5 dB

Question 23

Tripling the distance between sound source and a listener will change the intensity, as detected by the listener, by what factor?

A)1/9
B)0.33
C)3.0
D)9.0

Question 24

A phase difference of 270 $\degree$ corresponds to what wavelength difference?

A)3l
B)3l/2
C)3l/4
D)4l/3

Question 25

A plane is traveling at Mach 0.950 through air at a temperature of 0 $\degree$ C.What is the plane's speed? (Speed of sound at 0 $\degree$ C is 331 m/s.)

A)314 m/s
B)331 m/s
C)348 m/s
D)Mach number is undefined at 0 $\degree$ C.

Question 26

The Doppler shift of ultrasonic waves can measure the speed of blood in an artery.If the frequency of the stationary source is 100 kHz and the reflected sound has a Doppler shift of 200 Hz, what is the blood flow speed? (The speed of sound inside the body is 1 500 m/s.)

A)1.0 m/s
B)1.5 m/s
C)2.2 m/s
D)3.3 m/s

Question 27

You stand by the railroad tracks as a train passes by.You hear a 1 000-Hz frequency when the train approaches, which changes to 800 Hz as it goes away.How fast is the train moving? The speed of sound in air is 340 m/s.

A)15.7 m/s
B)21.2 m/s
C)28.0 m/s
D)37.8 m/s

Question 28

A 500-Hz whistle is moved toward a listener at a speed of 10.0 m/s.At the same time, the listener moves at a speed of 20.0 m/s in a direction away from the whistle.What is the apparent frequency heard by the listener? (The speed of sound is 340 m/s.)

A)473 Hz
B)485 Hz
C)533 Hz
D)547 Hz

Question 29

An airplane flying with a constant speed flies from a warm air mass into a cold air mass.The Mach number will:

A)increase.
B)decrease.
C)stay the same.
D)become unstable.

Question 30

In the afternoon, the decibel level of a busy freeway is 80 dB with 100 cars passing a given point every minute.Late at night, the traffic flow is only 5 cars per minute.What is the late-night decibel level?

A)77 dB
B)74 dB
C)70 dB
D)68 dB

Question 31

Two cars, one in front of the other, are traveling down the highway at 25 m/s.The car behind sounds its horn, which has a frequency of 500 Hz.What is the frequency heard by the driver of the lead car? (v_sound = 340 m/s)

A)463 Hz
B)540 Hz
C)579 Hz
D)500 Hz

Question 32

A bat, flying at 5.00 m/s toward a wall, emits a chirp at 50.0 kHz.If the wall reflects this sound pulse, what is the frequency of the echo received by the bat? (v_sound = 340 m/s)

A)51.5 kHz
B)51.2 kHz
C)40.8 kHz
D)50.5 kHz

Question 33

What is the intensity of sound from a band with a sound level of 120 dB? (I₀ = 10^-12 W/m²)

A)1 W/m²
B)1.2 W/m²
C)10 W/m²
D)12 W/m²

Question 34

A sound source of frequency 1 000 Hz moves at 50.0 m/s toward a listener who is at rest.What is the apparent frequency heard by the listener? (speed of sound = 340 m/s)

A)853 Hz
B)872 Hz
C)1 150 Hz
D)1 170 Hz

Question 35

The intensity level of sound 20 m from a jet airliner is 120 dB.At what distance from the airplane will the sound intensity level be a tolerable 100 dB? (Assume spherical spreading of sound.)

A)90 m
B)120 m
C)150 m
D)200 m

Question 36

What sound level change corresponds to a factor of two change in intensity?

A)0.5 dB
B)2 dB
C)3 dB
D)5 dB

Question 37

While standing at a crosswalk, you hear a frequency of 560 Hz from an approaching police car.After the police car passes, its frequency is 480 Hz.What is the speed of the police car? (speed of sound = 340 m/s)

A)13.1 m/s
B)17.4 m/s
C)21.1 m/s
D)26.2 m/s

Question 38

A very loud train whistle has an acoustic power output of 100 W.If the sound energy spreads out spherically, what is the intensity level in dB at a distance of 100 meters from the train? (I₀ = 10^-12 W/m²)

A)78.3 dB
B)81.6 dB
C)89.0 dB
D)95.0 dB

Question 39

A train station bell gives off a fundamental tone of 500 Hz as the train approaches the station at a speed of 20 m/s.If the speed of sound in air is 335 m/s, what will be the apparent frequency of the bell to an observer riding the train?

A)532 Hz
B)530 Hz
C)470 Hz
D)472 Hz

Question 40

As a train starts from rest and then accelerates down the track, coming toward me faster and faster, the speed of the sound waves coming toward me will be:

A)slower than the normal speed of sound in air.
B)equal to the normal speed of sound in air.
C)some constant speed faster than the normal speed of sound in air.
D)faster and faster.

Question 41

When two sound waves are out of phase by ____, destructive interference will occur.

A)90 $\degree$
B)270 $\degree$
C)540 $\degree$
D)720 $\degree$

Question 42

When I stand halfway between two speakers, with one on my left and one on my right, a musical note from the speakers gives me constructive interference.How far to my left should I move to obtain destructive interference?

A)one-fourth of a wavelength
B)half a wavelength
C)one wavelength
D)one and a half wavelengths

Question 43

A C note (f = 256 Hz) is sounded on a piano.If the length of the piano wire is 1.00 m and its mass density is 2.50 g/m, what is the tension in the wire?

A)84 N
B)168 N
C)655 N
D)1 280 N

Question 44

Two loudspeakers are placed side by side and driven by the same source at 500 Hz.A listener is positioned in front of the two speakers and on the line separating them, thus creating a constructive interference at the listener's ear.If one of the speakers is gradually pushed toward the listener, how far must it be moved to repeat the condition of constructive interference at the listener's ear? (The speed of sound = 340 m/s.)

A)1.02 m
B)0.68 m
C)0.34 m
D)0.17 m

Question 45

A child sits on a swing supported by ropes of length 3.0 m.With what frequency will she need to apply the driving force to maintain swinging?

A)0.29 Hz
B)0.48 Hz
C)2.1 Hz
D)3.5 Hz

Question 46

A standing wave is set up in a 2.0-m string fixed at both ends.The string vibrates in 5 distinct segments when driven by a 120-Hz source.In how many distinct standing wave segments will the string vibrate if the tension is increased by a factor of 4?

A)3
B)10
C)20
D)No standing wave pattern occurs.

Question 47

If I triple the mass per unit length of guitar string, its natural frequency changes by what factor?

A)0.58
B)1.0
C)1.7
D)3.0

Question 48

Doubling the tension in a guitar string will change its natural frequency by what factor?

A)0.71
B)1.0
C)1.4
D)2.0

Question 49

What is the lowest frequency that will resonate in an organ pipe 2.00 m in length, closed at one end? The speed of sound in air is 340 m/s.

A)42.5 Hz
B)85.0 Hz
C)170 Hz
D)680 Hz

Question 50

If the tension on a guitar string is increased by a factor of 3, the fundamental frequency at which it vibrates is changed by what factor?

A)9
B)3
C)
D)

Question 51

A standing wave is set up in a 200-cm string fixed at both ends.The string vibrates in 5 distinct segments when driven by a 120-Hz source.What is the wavelength?

A)10 cm
B)20 cm
C)40 cm
D)80 cm

Question 52

The lower A on a piano has a frequency of 27.5 Hz.If the tension in the 2.0-m-long string is 304 N and one-half wavelength occupies the string, what is the mass of the string?

A)100 g
B)25 g
C)37 g
D)50 g

Question 53

For a standing wave on a string the wavelength must equal:

A)the distance between adjacent nodes.
B)the distance between adjacent antinodes.
C)twice the distance between adjacent nodes.
D)the distance between supports.

Question 54

A 1.5-m string is held fixed at both ends.When driven by a 180-Hz source, the string vibrates in 4 distinct segments.What is the natural fundamental frequency of the string?

A)45 Hz
B)90 Hz
C)240 Hz
D)600 Hz

Question 55

A 100-m-long high-voltage cable is suspended between two towers.The mass of the 100-m cable is 150 kg.If the tension in the cable is 30 000 N, what is the lowest frequency at which this cable can oscillate?

A)0.71 Hz
B)1.0 Hz
C)1.4 Hz
D)2.0 Hz

Question 56

A 2.50-m-long organ pipe is open at one end and closed at the other.Its fundamental tone has wavelength:

A)1.25 m.
B)5.00 m.
C)10.0 m.
D)16.25 m.

Question 57

Two loudspeakers are placed next to each other and driven by the same source at 500 Hz.A listener is positioned in front of the two speakers and on the line separating them, thus creating a constructive interference at the listener's ear.What minimum distance would one of the speakers be moved back away from the listener to produce destructive interference at the listener's ear? (The speed of sound = 340 m/s.)

A)1.36 m
B)0.68 m
C)0.34 m
D)0.17 m

Question 58

I stretch a rubber band and "plunk" it to make it vibrate in its fundamental frequency.I then stretch it to twice its length and make it vibrate in the fundamental frequency once again.The rubber band is made so that doubling its length doubles the tension and reduces the mass per unit length by a factor of 2.The new frequency will be related to the old by a factor of:

A)1.0.
B)1.4.
C)2.0.
D)4.0.

Question 59

When the standing wave pattern in a pipe is NANA, the pipe has which of the following set of properties? (N stands for node, A for antinode.)

A)It is open at both ends.
B)It is closed at both ends.
C)It is open at one end and closed at the other end.
D)Any of the above could be true.

Question 60

If a guitar string has a fundamental frequency of 500 Hz, what is the frequency of its second overtone?

A)250 Hz
B)750 Hz
C)1 000 Hz
D)1 500 Hz

Question 61

In which part of the ear is the cochlea?

A)outer ear
B)middle ear
C)inner ear
D)ear canal

Question 62

The number of overtones, and their relative intensities, is associated with what property of the tone generated by a musical instrument?

A)quality
B)interference pattern
C)range
D)attack pattern

Question 63

Two vibrating tuning forks, held side by side, will create a beat frequency of what value if the individual frequencies of the two forks are 342 Hz and 345 Hz, respectively?

A)687 Hz
B)343.5 Hz
C)339 Hz
D)3 Hz

Question 64

If two adjacent frequencies of an organ pipe closed at one end are 550 Hz and 650 Hz, what is the length of the organ pipe? (v_sound = 340 m/s)

A)0.85 m
B)1.25 m
C)1.50 m
D)1.70 m

Question 65

What phenomenon is created by two tuning forks, side by side, emitting frequencies, which differ by only a small amount?

A)resonance
B)interference
C)the Doppler effect
D)beats

Question 66

The term "timbre" refers to which of the following?

A)Any musical instrument made primarily of wood.
B)The quality of sound from instruments due to the mixture of harmonics.
C)Instruments that have valves.
D)An instrument made in France.

Question 67

The air in a tube open at both ends is sent into its fundamental resonance.One end of the tube is then closed and the air column is again set into its fundamental resonance.The resonant frequency ____ after the end is closed.

A)halves
B)stays the same
C)doubles
D)increases by a factor of 1.4

Question 68

A buzzer with frequency f₀ is thrown straight upwards.On the buzzer's trip down, what is the frequency behavior heard by an observer below?

A)The frequency heard is still f₀.
B)The frequency is a constant one greater than f_0.
C)The frequency is an increasing one greater than f_0.
D)The frequency is a decreasing one less than f_0.

Question 69

Of the frequencies listed below, to which one is the human ear most sensitive?

A)33 Hz
B)330 Hz
C)3 300 Hz
D)33 000 Hz

Question 70

Which of the following best describes a sound level of intensity 1 W/m²?

A)extremely loud
B)about that of a power mower
C)normal conversation
D)like a whisper

Question 71

A vibrating guitar string emits a tone simultaneously with one from a 500-Hz tuning fork.If a beat frequency of 5 Hz results, what is the frequency of vibration of the string?

A)2 500 Hz
B)505 Hz
C)495 Hz
D)Either choice b or c is valid.

Question 72

Two tuning forks sounding together result in a beat frequency of 3 Hz.If the frequency of one of the forks is 256 Hz, what is the frequency of the other?

A)262 Hz or 250 Hz
B)105 Hz
C)259 Hz or 253 Hz
D)85 Hz

Question 73

The air in a pipe resonates at 150 Hz and 750 Hz, one of these resonances being the fundamental.If the pipe is open at both ends, how many resonances are between the two given ones, and if the pipe is closed at one end, how many resonances are between the two given ones?

A)open: 3; closed: 1
B)open: 1; closed: 3
C)open: 2; closed: 0
D)open: 0; closed: 2

Question 74

For a standing wave in an air column in a pipe that is open at both ends, there must be at least:

A)one node and one antinode.
B)two nodes and one antinode.
C)two antinodes and one node.
D)two nodes and two antinodes.

Question 75

How far away is a lightning bolt if it takes 10 s for the sound of the associated thunder to reach the observer?

A)1 mile
B)2 miles
C)5 miles
D)10 miles

Question 76

A flute behaves like a tube open at both ends.If its length is 65.3 cm, and the speed of sound is 340 m/s, what is its fundamental frequency in Hz?

A)130 Hz
B)159 Hz
C)212 Hz
D)260 Hz

Question 77

A tuning fork is sounded above a resonating tube (one end closed), which resonates at a length of 0.200 m and again at 0.600 m.What is the frequency of the fork when the speed of sound is taken to be 340 m/s?

A)567 Hz
B)425 Hz
C)1 700 Hz
D)950 Hz

Question 78

A tuning fork is sounded above a resonating tube (one end closed), which resonates at a length of 0.20 m and again at 0.60 m.If the tube length were extended further, at what point will the tuning fork again create a resonance condition?

A)0.8 m
B)1.0 m
C)1.2 m
D)1.6 m

Question 79

If the air temperature decreases, how does the resonant frequency in a pipe closed at one end change?

A)It increases.
B)It decreases.
C)It doesn't change since one end of the pipe is closed.
D)It doesn't change because resonance is pressure phenomenon.

Question 80

What is the first overtone frequency for an organ pipe 2.00 m in length, closed at one end? The speed of sound in air is 340 m/s.

A)42.5 Hz
B)85.0 Hz
C)128 Hz
D)680 Hz