Deck 12: Sound

Question 1

Choose the one alternative that best completes the statement or answers the question.
A certain glass window reduces the intensity level of the sound from 72 dB to 47 dB. By what factor is the acoustic power reduced by this glass window?

A) $1.5 \times 10 ^ { - 1 }$
B) $5.6 \times 10 ^ { - 2 }$
C) $3.2 \times 10 ^ { - 3 }$
D) $1.0 \times 10 ^ { - 1 }$
E) $2.2 \times 10 ^ { - 2 }$

Answer 1

C

Question 2

Write the word or phrase that best completes each statement or answers the question.
A long-term exposure to the sound of a riveting machine can cause your threshold of hearing to shift from 0 dB to 30 dB. What is the sound intensity of a 30-dB sound? The normal lowest detectable intensity is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

Answer 2

1.0 × 10-9 W/m2

Question 3

Write the word or phrase that best completes each statement or answers the question.
A factory siren indicating the end of a shift has a frequency of 80 Hz where the speed of
sound in air is 343 m/s. What frequency is perceived by the occupant of a car that is
traveling at 30 m/s (a) towards the factory and (b) away from the factory?

Answer 3

(a) 87 Hz (b) 73 Hz

Question 4

Choose the one alternative that best completes the statement or answers the question.
If the intensity level of one trombone is 70 dB, calculate a reasonable estimate for the intensity level of 76 trombones all playing simultaneously in the same place?

A) 70 dB
B) 146 dB
C) 89 dB
D) 82 dB
E) 76 dB

Question 5

Write the word or phrase that best completes each statement or answers the question.
A certain factory whistle can be heard up to a distance of 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

A) 2.6 mW
B) 0.026 mW
C) 0.079 mW
D) 0.26 mW
E) 0.79 mW

Question 6

Choose the one alternative that best completes the statement or answers the question.
Two people are talking at a distance of 3.0 m from where you are, and you measure the sound intensity as $1.1 \times 10 ^ { - 7 } \mathrm {~W} / \mathrm { m } ^ { 2 }$
Another student is 4.0 m away from the talkers. Calculate a reasonable estimate for the sound intensity that the other student measures.

A) $2.5 \times 10 ^ { - 8 } \mathrm {~W} / \mathrm { m } ^ { 2 }$
B) $7.8 \times 10 ^ { - 7 } \mathrm {~W} / \mathrm { m } ^ { 2 }$
C) $1.5 \times 10 ^ { - 7 } \mathrm {~W} / \mathrm { m } ^ { 2 }$
D) $8.3 \times 10 ^ { - 8 } \mathrm {~W} / \mathrm { m } ^ { 2 }$
E) $6.2 \times 10 ^ { - 8 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

Question 7

Write the word or phrase that best completes each statement or answers the question.
A plucked guitar string produces a sound wave of frequency 0.44 kHz on a day when the
speed of sound is 340 m/s.
(a) What is the wavelength of the sound wave?
(b) How much time elapses between the impacts of two adjacent compressions of the
sound wave on your eardrum?

Question 8

Write the word or phrase that best completes each statement or answers the question.
A standing wave of the third overtone is induced in a 1.2-m pipe that is open at one end
and closed at the other end. The speed of sound in the pipe is 340 m/s.
(a) How many antinodes are there in the standing wave pattern?
(b) What is the frequency of the sound produced by the pipe in this situation?

Question 9

Write the word or phrase that best completes each statement or answers the question.
An organ pipe that is 1.75 m long and open at both ends produces sound of frequency 303
Hz when resonating in its second overtone. What is the speed of sound in the room?

Question 10

Choose the one alternative that best completes the statement or answers the question.
What is the intensity level in decibels of a sound with intensity The threshold of human hearing is

A) 96 dB
B) 90 dB
C) 30 dB
D) 60 dB

Question 11

Choose the one alternative that best completes the statement or answers the question.
What is the intensity of a 70-dB sound? The threshold of human hearing is

A)
B)
C)
D)

Question 12

Write the word or phrase that best completes each statement or answers the question.
An organ pipe closed at one end and open at the other end has two successive harmonics
with frequencies of 2170 Hz and 2790 Hz. What is the fundamental frequency of the pipe?

Question 13

Choose the one alternative that best completes the statement or answers the question.
The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is
What is the power emitted by the source?

A)
B)
C)
D)

Question 14

Write the word or phrase that best completes each statement or answers the question.
A certain factory whistle can be heard up to a distance of 9.8 km. Assuming that the acoustic output of the whistle is uniform in all directions, at what distance from the factory is the intensity level of the whistle sound equal to 25 dB? The threshold of human hearing is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

A) 940 m
B) 1100 m
C) 830 m
D) 550 m
E) 660 m

Question 15

Write the word or phrase that best completes each statement or answers the question.
As shown in the figure, a man is traveling on a bicycle along a straight road that runs
parallel to and right next to some railroad tracks. While moving at 10 m/s, he hears the
whistle of a train that is behind him, as shown in the figure. The frequency emitted by the
train's whistle is 820 Hz, but the frequency the man hears is 774 Hz. The speed of sound is
340 m/s.
(a) What frequency is heard by a stationary observer located between the train and the
bicycle?
(b) What is the speed of the train, and is the train traveling away from or toward the
bicycle?

Question 16

Choose the one alternative that best completes the statement or answers the question.
A pipe that is 0.92 m long and open at both ends vibrates in the second overtone with a frequency of 584 Hz. What is the speed of sound in the air in this pipe?

A) 363 m/s
B) 349 m/s
C) 344 m/s
D) 358 m/s
E) 353 m/s

Question 17

Choose the one alternative that best completes the statement or answers the question.
A crying baby emits sound with an intensity of $8.0 \times 10 ^ { - 8 } \mathrm {~W} / \mathrm { m } ^ { 2 }$ Calculate a reasonable estimate for the intensity level from a set of quintuplets (five babies), all crying simultaneously at the same place? The lowest detectable intensity is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

A) 49 dB
B) 36 dB
C) 56 dB
D) 69 dB
E) 79 dB

Question 18

Write the word or phrase that best completes each statement or answers the question.
A certain siren radiates sound uniformly in all directions. At a distance of 17 m from the siren, the intensity level is 49 db. How many watts of power does this siren put out? The threshold of human hearing is $1.0 \times 10 ^ { - 12 } \mathrm {~W} / \mathrm { m } ^ { 2 }$

Question 19

Write the word or phrase that best completes each statement or answers the question.
An elephant can hear sound with a frequency of 15 Hz. What is the wavelength of this
wave if the speed of sound in air is 343 m/s?

Question 20

Write the word or phrase that best completes each statement or answers the question.
Two police cars have identical sirens that produce sound of frequency of 570 Hz. A
stationary listener is standing between two cars. One car is parked and the other is
approaching the listener and both have their sirens on. The listener measures 9.0 beats per
second. Find the speed of the approaching police car. The speed of sound is 340 m/s.

Question 21

Write the word or phrase that best completes each statement or answers the question.
A jet flies at 1.4 times the speed of sound. What is the half-angle of the conical shock wave formed?

A) $30 ^ { \circ }$
B) $36 ^ { \circ }$
C) $46 ^ { \circ }$
D) $44 ^ { \circ }$