Question 1

An organ pipe open at both ends has two successive harmonics with frequencies of 210 Hz and 240 Hz. What is the length of the pipe? The speed of sound is 344 m/s in air.

Accepted Answer

A)  5.25 m 
B)  5.73 m 
C)  2.76 m 
D)  4.90 m 
E)  3.62 m 
A)  5.25 m 
B)  5.73 m 
C)  2.76 m 
D)  4.90 m 
E)  3.62 m

Question 2

Two pure tones are sounded together and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

Accepted Answer

A)  It increases. 
B)  It decreases. 
C)  It does not change. 
D)  It becomes zero. 
E)  We cannot tell from the information given. 
A)  It increases. 
B)  It decreases. 
C)  It does not change. 
D)  It becomes zero. 
E)  We cannot tell from the information given.

Question 3

Two loudspeakers placed 6.0 m apart are driven in phase by an audio oscillator whose frequency range is 2193 Hz to 2967 Hz. A point P is located 4.4 m from one loudspeaker and 3.6 m from the other. The speed of sound is 344 m/s. The frequency produced by the oscillator, for which constructive interference of sound occurs at point P, is closest to

Accepted Answer

A)  2580 Hz. 
B)  2903 Hz. 
C)  2473 Hz. 
D)  2795 Hz. 
E)  2688 Hz. 
A)  2580 Hz. 
B)  2903 Hz. 
C)  2473 Hz. 
D)  2795 Hz. 
E)  2688 Hz.

Question 4

A factory siren indicating the end of a shift has a frequency of 90.0 Hz. The speed of sound is 343 m/s.
(a) What frequency is perceived by the occupant of a car traveling towards the factory at 25.0 m/s?
(b) What frequency is perceived by the occupant of a car traveling away from the factory at 30.0 m/s?

Accepted Answer

(a) 96.6 H

Question 5

A bat emits a sound at a frequency of 30.0 kHz as it approaches a wall. The bat detects beats such that the frequency of the echo is 900 Hz higher than the frequency the bat is emitting. The speed of sound in air is 340 m/s. The speed of the bat is closest to

Accepted Answer

A)  20.0 m/s. 
B)  530 m/s. 
C)  10.0 m/s. 
D)  30.0 m/s. 
E)  5.02 m/s. 
A)  20.0 m/s. 
B)  530 m/s. 
C)  10.0 m/s. 
D)  30.0 m/s. 
E)  5.02 m/s.

Question 6

A woman is riding a bicycle at 18.0 m/s along a straight road that runs parallel to and right next to some railroad tracks. She hears the whistle of a train that is behind. The frequency emitted by the train is 840 Hz, but the frequency the woman hears is 778 Hz. Take the speed of sound to be 340 m/s.
(a) What is the speed of the train, and is the train traveling away from or toward the bicycle?
(b) What frequency is heard by a stationary observer located between the train and the bicycle?

Accepted Answer

(a) 7.67 m

Question 7

In a resonating pipe that is open at both ends, there

Accepted Answer

A)  are displacement nodes at each end. 
B)  are displacement antinodes at each end. 
C)  is a displacement node at one end and a displacement antinode at the other end. 
D)  None of the above are possible. 
A)  are displacement nodes at each end. 
B)  are displacement antinodes at each end. 
C)  is a displacement node at one end and a displacement antinode at the other end. 
D)  None of the above are possible.

Question 8

A certain source of sound waves radiates uniformly in all directions. At a distance of 20 m from the source the intensity level is 51 db. What is the total acoustic power output of the source, in watts? (Note: The reference intensity I0 is 1.0 × 10-12 W/m2.)

Accepted Answer

Question 9

Two identical loudspeakers that are 5.00 m apart and face toward each other are driven in phase by the same oscillator at a frequency of 875 Hz. The speed of sound in the room is 344 m/s. If you start out standing midway between the speakers, find the shortest distance you can walk toward either speaker in order to hear a minimum of sound.

Accepted Answer

A)  0.0983 m 
B)  0.197 m 
C)  0.295 m 
D)  0.393 m 
E)  0.590 m 
A)  0.0983 m 
B)  0.197 m 
C)  0.295 m 
D)  0.393 m 
E)  0.590 m

Question 10

A string, 0.28 m long and vibrating in its third harmonic, excites an open pipe that is 0.82 m long into its second overtone resonance. The speed of sound in air is 345 m/s. The speed of transverse waves on the string is closest to

Accepted Answer

A)  120 m/s. 
B)  110 m/s. 
C)  100 m/s. 
D)  98 m/s. 
E)  91 m/s. 
A)  120 m/s. 
B)  110 m/s. 
C)  100 m/s. 
D)  98 m/s. 
E)  91 m/s.

Question 11

A string 40.0 cm long of mass 8.50 g is fixed at both ends and is under a tension of 425 N. When this string is vibrating in its third OVERTONE, you observe that it causes a nearby pipe, open at both ends, to resonate in its third HARMONIC. The speed of sound in the room is 344 m/s.
(a) How long is the pipe?
(b) What is the fundamental frequency of the pipe?

Accepted Answer

(a) 0.730

Question 12

Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 1536 Hz. You move between the speakers, along the line joining them, at a constant speed of 2.8 m/s. What beat frequency do you observe? The speed of sound in the room is 330 m/s.

Accepted Answer

A)  13 Hz 
B)  431 Hz 
C)  26 Hz 
D)  4.7 Hz 
E)  118 Hz 
A)  13 Hz 
B)  431 Hz 
C)  26 Hz 
D)  4.7 Hz 
E)  118 Hz

Question 13

A violin with string length 32 cm and string density 1.5 g/cm resonates with the first overtone from a 2.0-m long organ pipe with one end closed and the other end open. What is the tension in the string?

Accepted Answer

A)  1000 N 
B)  110 N 
C)  450 N 
D)  4100 N 
E)  56 N 
A)  1000 N 
B)  110 N 
C)  450 N 
D)  4100 N 
E)  56 N

Question 14

A pipe that is 20.0 m long and 10.0 cm in diameter contains olive oil. The density of the olive oil is 890 kg/m3 and the bulk modulus is 1.3 × 109 Pa. A 3.4-Hz longitudinal wave is transmitted in the oil. How many milliseconds does it take for the wave to travel the length of the pipe in the oil?

Accepted Answer

A)  17 ms 
B)  15 ms 
C)  14 ms 
D)  13 ms 
E)  12 ms 
A)  17 ms 
B)  15 ms 
C)  14 ms 
D)  13 ms 
E)  12 ms

Question 15

Shock waves occur when

Accepted Answer

A)  the frequency of the waves is the resonant frequency of the system. 
B)  the amplitude of waves exceeds the critical shock value. 
C)  two waves from different sources collide with each other. 
D)  the wave source is traveling at a speed greater than the wave speed. 
E)  the period of the waves matches the lifetime of the waves. 
A)  the frequency of the waves is the resonant frequency of the system. 
B)  the amplitude of waves exceeds the critical shock value. 
C)  two waves from different sources collide with each other. 
D)  the wave source is traveling at a speed greater than the wave speed. 
E)  the period of the waves matches the lifetime of the waves.

Question 16

A howler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 5.0 km. Assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10-12 W/m2. The acoustic power emitted by the howler is closest to

Accepted Answer

A)  0.31 mW. 
B)  0.11 mW. 
C)  1.1 mW. 
D)  3.2 mW. 
E)  11 mW. 
A)  0.31 mW. 
B)  0.11 mW. 
C)  1.1 mW. 
D)  3.2 mW. 
E)  11 mW.

Question 17

A carousel that is 5.00 m in radius has a pair of 600-Hz sirens mounted on posts at opposite ends of a diameter. The carousel rotates with an angular velocity of 0.800 rad/s. A stationary listener is located at a distance from the carousel. The speed of sound is 350 m/s. The longest wavelength reaching the listener from the sirens is closest to

Accepted Answer

A)  57.0 cm. 
B)  57.7 cm. 
C)  58.3 cm. 
D)  59.0 cm. 
E)  59.6 cm. 
A)  57.0 cm. 
B)  57.7 cm. 
C)  58.3 cm. 
D)  59.0 cm. 
E)  59.6 cm.

Question 18

At a distance of 2.00 m from a point source of sound, the intensity level is 80.0 dB. What will be the intensity level at a distance of 4.00 m from this source? The lowest detectable intensity is 1.0 × 10-12 W/m2.

Accepted Answer

A)  77.0 dB 
B)  74.0 dB 
C)  60.0 dB 
D)  40.0 dB 
E)  20.0 dB 
A)  77.0 dB 
B)  74.0 dB 
C)  60.0 dB 
D)  40.0 dB 
E)  20.0 dB

Question 19

An air column, open at one end and closed at the other, is being designed so that its second lowest resonant frequency is 440 Hz. What should be the length of the column if the speed of sound in air is 340 m/s?

Accepted Answer

A)  0.386 m 
B)  0.772 m 
C)  1.16 m 
D)  0.193 m 
E)  0.580 m 
A)  0.386 m 
B)  0.772 m 
C)  1.16 m 
D)  0.193 m 
E)  0.580 m

Question 20

Radio station KBOB broadcasts at a frequency of 85.7 MHz on your dial using radio waves that travel at 3.00 × 108 m/s. Since most of the station's audience is due south of the transmitter, the managers of KBOB don't want to waste any energy broadcasting to the east and west. They decide to build two towers, transmitting in phase at exactly the same frequency, aligned on an east-west axis. For engineering reasons, the two towers must be AT LEAST 10.0 m apart. What is the shortest distance between the towers that will eliminate all broadcast power to the east and west?

Accepted Answer

Exam 15: Sound and Hearing

An organ pipe open at both ends has two successive harmonics with frequencies of 210 Hz and 240 Hz. What is the length of the pipe? The speed of sound is 344 m/s in air.

Two pure tones are sounded together and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

A bat emits a sound at a frequency of 30.0 kHz as it approaches a wall. The bat detects beats such that the frequency of the echo is 900 Hz higher than the frequency the bat is emitting. The speed of sound in air is 340 m/s. The speed of the bat is closest to

In a resonating pipe that is open at both ends, there

A certain source of sound waves radiates uniformly in all directions. At a distance of 20 m from the source the intensity level is 51 db. What is the total acoustic power output of the source, in watts? (Note: The reference intensity I0 is 1.0 × 10-12 W/m2.)

A string, 0.28 m long and vibrating in its third harmonic, excites an open pipe that is 0.82 m long into its second overtone resonance. The speed of sound in air is 345 m/s. The speed of transverse waves on the string is closest to

Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 1536 Hz. You move between the speakers, along the line joining them, at a constant speed of 2.8 m/s. What beat frequency do you observe? The speed of sound in the room is 330 m/s.

A violin with string length 32 cm and string density 1.5 g/cm resonates with the first overtone from a 2.0-m long organ pipe with one end closed and the other end open. What is the tension in the string?

A pipe that is 20.0 m long and 10.0 cm in diameter contains olive oil. The density of the olive oil is 890 kg/m3 and the bulk modulus is 1.3 × 109 Pa. A 3.4-Hz longitudinal wave is transmitted in the oil. How many milliseconds does it take for the wave to travel the length of the pipe in the oil?

Shock waves occur when

A howler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 5.0 km. Assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10-12 W/m2. The acoustic power emitted by the howler is closest to

At a distance of 2.00 m from a point source of sound, the intensity level is 80.0 dB. What will be the intensity level at a distance of 4.00 m from this source? The lowest detectable intensity is 1.0 × 10-12 W/m2.

An air column, open at one end and closed at the other, is being designed so that its second lowest resonant frequency is 440 Hz. What should be the length of the column if the speed of sound in air is 340 m/s?

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A certain source of sound waves radiates uniformly in all directions. At a distance of 20 m from the source the intensity level is 51 db. What is the total acoustic power output of the source, in watts? (Note: The reference intensity I0 is 1.0 × 10-12 W/m².)

A howler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 5.0 km. Assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10^-12W/m². The acoustic power emitted by the howler is closest to

At a distance of 2.00 m from a point source of sound, the intensity level is 80.0 dB. What will be the intensity level at a distance of 4.00 m from this source? The lowest detectable intensity is 1.0 × 10^-12 W/m².