Question 1

You are in a dark cave; suddenly you hear screeching sounds that are increasing in pitch. From this you discern that something is

Accepted Answer

A)  coming toward you. 
B)  going away from you. 
C)  remaining stationary. 
D)  none of the above. 
A)  coming toward you. 
B)  going away from you. 
C)  remaining stationary. 
D)  none of the above. A

Question 2

A police car sounds its siren, which has a true frequency of 600 Hz, as it leaves the police station. If the police car is traveling at 35 m/s away from the station, the frequency of the siren as heard by listeners back at the station is (use 344 m/s for the speed of sound)

Accepted Answer

A)  668 Hz. 
B)  545 Hz. 
C)  621 Hz. 
D)  582 Hz. 
A)  668 Hz. 
B)  545 Hz. 
C)  621 Hz. 
D)  582 Hz. B

Question 3

All of the following "pairs" are measured or expressed in terms of a logarithmic scale except

Accepted Answer

A)  intensity level-decibel. 
B)  musical scale-octave. 
C)  Richter scale-magnitude. 
D)  none of the above. 
A)  intensity level-decibel. 
B)  musical scale-octave. 
C)  Richter scale-magnitude. 
D)  none of the above. D

Question 4

The primary reason for the correct answer to the previous question is that

Accepted Answer

A)  the restoring force for solids is > the restoring force for air at atmospheric pressure. 
B)  the density of solids is > the density of air. 
C)  the effect of the first answer to this question predominates over the effect of the second answer. 
D)  the effect of the second answer to this question predominates over the effect of the first answer. 
A)  the restoring force for solids is > the restoring force for air at atmospheric pressure. 
B)  the density of solids is > the density of air. 
C)  the effect of the first answer to this question predominates over the effect of the second answer. 
D)  the effect of the second answer to this question predominates over the effect of the first answer.

Question 5

The intensity of sound (W/m $2$ ) varies as

Accepted Answer

A)  the power squared. 
B)  1 over the power. 
C)  1 over the power squared. 
D)  the power. 
A)  the power squared. 
B)  1 over the power. 
C)  1 over the power squared. 
D)  the power.

Question 6

An astute physics student is near a train track. As a train speeds by, the perceived frequency of the whistle changes from middle C to the A below middle C. If the initial perceived frequency of the whistle had been an octave above middle C, as the train whizzed by the frequency would have changed to

Accepted Answer

A) the A above middle C. B) a frequency > the A above middle C. C) a frequency < the A above middle C. D) none of the above. A) the A above middle C. B) a frequency > the A above middle C. C) a frequency < the A above middle C. D) none of the above.

Question 7

A listener records a sound intensity of 12 W/m $2$ from a 250-W loudspeaker. The loudspeaker emits sound uniformly in all directions. The distance from the loudspeaker to the listener is

Accepted Answer

A)  2.6 m. 
B)  5.2 m. 
C)  1.3 m. 
D)  4.1 m. 
A)  2.6 m. 
B)  5.2 m. 
C)  1.3 m. 
D)  4.1 m.

Question 8

The speed of earthquake waves near the surface of the Earth is on the order of 10 times the speed of sound in air. Periods are on the order of a second. Therefore, the distance between "crests" for these waves is on the order of

Accepted Answer

A)  a fraction of an inch. 
B)  a foot. 
C)  several hundred feet. 
D)  a mile. 
A)  a fraction of an inch. 
B)  a foot. 
C)  several hundred feet. 
D)  a mile.

Question 9

A stationary emitter generates a sound of frequency $V$ . The frequency shift $\delta v _ { \gamma }$ if the receiver is moving at a speed that is not < the speed of sound in still air is related to the frequency shift $\delta v _ { e }$ if the emitter moves at precisely the same speed (in the appropriate direction) with respect to a stationary receiver by the relation

Accepted Answer

A) $V _ { y } > V _ { e }$ B) $V _ { y } = V _ { e }$ C) $V _ { y } < V _ { e }$ D) none of the above. A) $V _ { y } > V _ { e }$ B) $V _ { y } = V _ { e }$ C) $V _ { y } < V _ { e }$ D) none of the above.

Question 10

A (point-source) loudspeaker produces an average intensity of 56.8 W/m $2$ at two meters away. The output power of the loudspeaker is

Accepted Answer

A)  2900 W. 
B)  1200 W. 
C)  710 W. 
D)  580 W. 
A)  2900 W. 
B)  1200 W. 
C)  710 W. 
D)  580 W.

Question 11

The speed of water waves in deep water depends on the two parameters

Accepted Answer

A)  gravity and wavelength. 
B)  gravity and water depth. 
C)  wavelength and water depth. 
D)  none of the above. 
A)  gravity and wavelength. 
B)  gravity and water depth. 
C)  wavelength and water depth. 
D)  none of the above.

Question 12

As the velocity of a jet approaches infinity, the Mach half-angle becomes

Accepted Answer

A)  90º. 
B)  0º. 
C)  45º. 
D)  30º. 
A)  90º. 
B)  0º. 
C)  45º. 
D)  30º.

Question 13

A stationary emitter generates a sound at some particular frequency. The frequency detected by a receiver moving away from the emitter at speed vr (< the speed of sound in still air) is roughly the same as if the

Accepted Answer

A)  emitter were to move at the same speed vr away from a stationary receiver. 
B)  emitter were to move at the same speed vr toward a stationary receiver. 
C)  receiver were to move at the same speed vr toward a stationary receiver. 
D)  none of the above. 
A)  emitter were to move at the same speed vr away from a stationary receiver. 
B)  emitter were to move at the same speed vr toward a stationary receiver. 
C)  receiver were to move at the same speed vr toward a stationary receiver. 
D)  none of the above.

Question 14

The angle $\theta$ that the wave front of a Mach cone makes with the direction of travel of a supersonic aircraft is related to the speed of sound v and the speed of the supersonic aircraft (emitter) VE by the formula

Accepted Answer

A)  VE = v cos $\theta$ 
B)  v = VE cos $\theta$ 
C)  VE = v sin $\theta$ 
D)  v = VE sin $\theta$ 
A)  VE = v cos $\theta$ 
B)  v = VE cos $\theta$ 
C)  VE = v sin $\theta$ 
D)  v = VE sin $\theta$

Question 15

The intensity I of a wave is related to the distance the wave travels by the expression I ? 18 1/r2. The assumptions on which this formula depend include all of the following except

Accepted Answer

A)  the wave energy travels outward into three-dimensional space. 
B)  the medium is homogeneous. 
C)  the medium is nonabsorptive. 
D)  none of the above. 
A)  the wave energy travels outward into three-dimensional space. 
B)  the medium is homogeneous. 
C)  the medium is nonabsorptive. 
D)  none of the above.

Question 16

Under ideal conditions, if a receiver and an emitter are both at rest with respect to the ground and a wind is blowing from receiver to emitter, the received frequency $V _ { y }$ will be related to the emitted frequency $V _ { E }$ by the expression

Accepted Answer

A) $V _ { y } > V _ { E }$ B) $V _ { y } = V _ { E }$ C) $V _ { y } < V _ { E }$ D) none of the above. A) $V _ { y } > V _ { E }$ B) $V _ { y } = V _ { E }$ C) $V _ { y } < V _ { E }$ D) none of the above.

Question 17

The wavelength of a 1000-Hz tone is (use 344 m/s for the speed of sound)

Accepted Answer

A)  3.1 m. 
B)  4.5 m. 
C)  34 cm. 
D)  82 cm. 
A)  3.1 m. 
B)  4.5 m. 
C)  34 cm. 
D)  82 cm.

Question 18

Consider a listener who is a distance $x$ from a loudspeaker. If the listener moves in so that her distance is now $x / 2$ from the loudspeaker, by what factor will the intensity of the sound increase?

Accepted Answer

A)  2 
B)  3 
C)  1.5 
D)  4 
A)  2 
B)  3 
C)  1.5 
D)  4

Question 19

The wavelength of tsunamis in midocean is on the order of several hundred miles. The speed of tsunami waves near the middle of the ocean is on the order of the speed of sound in air. Therefore, the time between successive crests for a ship in midocean that encounters a tsunami is on the order of

Accepted Answer

A)  a day. 
B)  an hour. 
C)  a minute. 
D)  a second. 
A)  a day. 
B)  an hour. 
C)  a minute. 
D)  a second.

Question 20

The intensity of sound when integrated over any Gaussian surface ( $\int I d A$ ) that encloses the source yields

Accepted Answer

A)  a conserved quantity. 
B)  the pressure. 
C)  a nonconserved quantity. 
D)  none of the above. 
A)  a conserved quantity. 
B)  the pressure. 
C)  a nonconserved quantity. 
D)  none of the above.

Exam 17: Sound

You are in a dark cave; suddenly you hear screeching sounds that are increasing in pitch. From this you discern that something is

A police car sounds its siren, which has a true frequency of 600 Hz, as it leaves the police station. If the police car is traveling at 35 m/s away from the station, the frequency of the siren as heard by listeners back at the station is (use 344 m/s for the speed of sound)

All of the following "pairs" are measured or expressed in terms of a logarithmic scale except

The primary reason for the correct answer to the previous question is that

The intensity of sound (W/m 222 ) varies as

A listener records a sound intensity of 12 W/m 222 from a 250-W loudspeaker. The loudspeaker emits sound uniformly in all directions. The distance from the loudspeaker to the listener is

The speed of earthquake waves near the surface of the Earth is on the order of 10 times the speed of sound in air. Periods are on the order of a second. Therefore, the distance between "crests" for these waves is on the order of

A (point-source) loudspeaker produces an average intensity of 56.8 W/m 222 at two meters away. The output power of the loudspeaker is

The speed of water waves in deep water depends on the two parameters

As the velocity of a jet approaches infinity, the Mach half-angle becomes

A stationary emitter generates a sound at some particular frequency. The frequency detected by a receiver moving away from the emitter at speed vr (< the speed of sound in still air) is roughly the same as if the

The angle θ\thetaθ that the wave front of a Mach cone makes with the direction of travel of a supersonic aircraft is related to the speed of sound v and the speed of the supersonic aircraft (emitter) VE by the formula

The intensity I of a wave is related to the distance the wave travels by the expression I ? 18 1/r2. The assumptions on which this formula depend include all of the following except

Under ideal conditions, if a receiver and an emitter are both at rest with respect to the ground and a wind is blowing from receiver to emitter, the received frequency VyV _ { y }Vy​ will be related to the emitted frequency VEV _ { E }VE​ by the expression

The wavelength of a 1000-Hz tone is (use 344 m/s for the speed of sound)

Consider a listener who is a distance xxx from a loudspeaker. If the listener moves in so that her distance is now x/2x / 2x/2 from the loudspeaker, by what factor will the intensity of the sound increase?

The wavelength of tsunamis in midocean is on the order of several hundred miles. The speed of tsunami waves near the middle of the ocean is on the order of the speed of sound in air. Therefore, the time between successive crests for a ship in midocean that encounters a tsunami is on the order of

The intensity of sound when integrated over any Gaussian surface ( ∫IdA\int I d A∫IdA ) that encloses the source yields

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The intensity of sound (W/m $2$ ) varies as

A listener records a sound intensity of 12 W/m $2$ from a 250-W loudspeaker. The loudspeaker emits sound uniformly in all directions. The distance from the loudspeaker to the listener is

A (point-source) loudspeaker produces an average intensity of 56.8 W/m $2$ at two meters away. The output power of the loudspeaker is

A stationary emitter generates a sound at some particular frequency. The frequency detected by a receiver moving away from the emitter at speed v_r(< the speed of sound in still air) is roughly the same as if the

The angle $\theta$ that the wave front of a Mach cone makes with the direction of travel of a supersonic aircraft is related to the speed of sound v and the speed of the supersonic aircraft (emitter) V_Eby the formula

The intensity I of a wave is related to the distance the wave travels by the expression I ? 18 1/r². The assumptions on which this formula depend include all of the following except

Under ideal conditions, if a receiver and an emitter are both at rest with respect to the ground and a wind is blowing from receiver to emitter, the received frequency $V _ { y }$ will be related to the emitted frequency $V _ { E }$ by the expression

Consider a listener who is a distance $x$ from a loudspeaker. If the listener moves in so that her distance is now $x / 2$ from the loudspeaker, by what factor will the intensity of the sound increase?

The intensity of sound when integrated over any Gaussian surface ( $\int I d A$ ) that encloses the source yields