Question 1

A spherical wave has the form  
)
The velocity of the wave (in m/s)is

Accepted Answer

A) 0.005 88. 
B) 16.0 
C) 340. 
D) 1 360. 
E) 2 720. 
A) 0.005 88. 
B) 16.0 
C) 340. 
D) 1 360. 
E) 2 720. C

Question 2

While you are sounding a tone on a toy whistle,you notice a friend running toward you.If you want her to hear the same frequency that you hear even though she is approaching,you must

Accepted Answer

A) stay put. 
B) run towards her at the same speed. 
C) run away from her at the same speed. 
D) stay put and play a note of higher frequency. 
E) run towards her and play a note of higher frequency. 
A) stay put. 
B) run towards her at the same speed. 
C) run away from her at the same speed. 
D) stay put and play a note of higher frequency. 
E) run towards her and play a note of higher frequency. C

Question 3

A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction.If the frequency of the siren is 500 Hz relative to the police car,what is the frequency heard by an observer in the truck after the police car passes the truck? (The speed of sound in air is 343 m/s. )

Accepted Answer

A) 361 
B) 636 
C) 393 
D) 396 
E) 383 
A) 361 
B) 636 
C) 393 
D) 396 
E) 383 D

Question 4

By what factor is the intensity of sound at a rock concert louder than that of a whisper when the two intensity levels are 120 dB and 20 dB respectively?

Accepted Answer

A) 1012 
B) 108 
C) 106 
D) 1010 
E) 1011 
A) 1012 
B) 108 
C) 106 
D) 1010 
E) 1011

Question 5

A person standing in the street is unaware of a bird dropping that is falling from a point directly above him with increasing velocity.If the dropping were producing sound of a fixed frequency,as it approaches the person would hear the sound

Accepted Answer

A) drop in frequency. 
B) stay at the same frequency. 
C) increase in frequency. 
D) decrease in loudness. 
E) stay at the same loudness. 
A) drop in frequency. 
B) stay at the same frequency. 
C) increase in frequency. 
D) decrease in loudness. 
E) stay at the same loudness.

Question 6

A sculptor strikes a piece of marble with a hammer.Find the speed of sound through the marble (in km/s).(The Young's modulus is 50 × 109 N/m2 and its density is 2.7 × 103 kg/m3. )

Accepted Answer

A) 5.1 
B) 4.3 
C) 3.5 
D) 1.3 
E) 1.8 
A) 5.1 
B) 4.3 
C) 3.5 
D) 1.3 
E) 1.8

Question 7

A spherical wave has the form  
)
The wavelength of the wave is

Accepted Answer

A) 0.25 m. 
B) 0.50 m. 
C) 4.0 m. 
D) 8.0 m. 
E) 4.0π m. 
A) 0.25 m. 
B) 0.50 m. 
C) 4.0 m. 
D) 8.0 m. 
E) 4.0π m.

Question 8

To decrease the intensity of the sound you are hearing from your speaker system by a factor of 36,you can

Accepted Answer

A) reduce the amplitude by a factor of 12 and increase your distance from the speaker by a factor of 3. 
B) reduce the amplitude by a factor of 4 and increase your distance from the speaker by a factor of 3. 
C) reduce the amplitude by a factor of 2 and increase your distance from the speaker by a factor of 3. 
D) reduce the amplitude by a factor of 3 and increase your distance from the speaker by a factor of 4. 
E) reduce the amplitude by a factor of 3 and increase your distance from the speaker by a factor of 12. 
A) reduce the amplitude by a factor of 12 and increase your distance from the speaker by a factor of 3. 
B) reduce the amplitude by a factor of 4 and increase your distance from the speaker by a factor of 3. 
C) reduce the amplitude by a factor of 2 and increase your distance from the speaker by a factor of 3. 
D) reduce the amplitude by a factor of 3 and increase your distance from the speaker by a factor of 4. 
E) reduce the amplitude by a factor of 3 and increase your distance from the speaker by a factor of 12.

Question 9

When a workman strikes a steel pipeline with a hammer,he generates both longitudinal and transverse waves.The two types of reflected waves return 2.4 s apart.How far away is the reflection point? (For steel,vL = 6.2 km/s,vT = 3.2 km/s)

Accepted Answer

Question 10

It is possible to hear an approaching train before you can see it by listening to the sound wave through the track.If the elastic modulus is 2.0 × 1011 N/m2 and the density of steel is 7.8 × 103 kg/m3,approximately how many times faster is the speed of sound in the track than in air? (vair ≈ 340 m/s. )

Accepted Answer

A) 20 
B) 5 
C) 10 
D) 15 
E) 25 
A) 20 
B) 5 
C) 10 
D) 15 
E) 25

Question 11

An airplane traveling at half the speed of sound emits sound at a frequency of 5 000 Hz.At what frequency does a stationary listener hear the sound as the plane approaches,and after it passes by? Assume the airplane is not flying very high.

Accepted Answer

The answer of An airplane traveling at half the speed...

Question 12

A source of sound waves is placed at the center of a very large sound-reflecting wall.The source emits 0.500 W of power.Two meters from the source the intensity in W/m2 is

Accepted Answer

A) 9.95 × 10−3. 
B) 1.99 × 10−2. 
C) 0.313. 
D) 0.399. 
E) 0.625. 
A) 9.95 × 10−3. 
B) 1.99 × 10−2. 
C) 0.313. 
D) 0.399. 
E) 0.625.

Question 13

A boat sounds a fog horn on a day when both the sea water and the air temperature are 25.0° C.The speed of sound in sea water is 1 533 m/s.How much earlier (in s)does a dolphin 1 000 m from the source hear the sound than a person in a boat that is also 1 000 m distant? (Ignore the time it takes the sound to reach the water surface. )

Accepted Answer

A) 0.652 
B) 2.12 
C) 2.24 
D) 2.77 
E) 2.90 
A) 0.652 
B) 2.12 
C) 2.24 
D) 2.77 
E) 2.90

Question 14

The variation in the pressure of helium gas,measured from its equilibrium value,is given by ΔP = 2.9 × 10−5 cos (6.20x − 3 000t)where x and t have units m and s,and ΔP is measured in N/m2.Determine the wavelength (in m)of the wave.

Accepted Answer

A) 1 500 
B) 0.32 
C) 477 
D) 1.01 
E) 0.50 
A) 1 500 
B) 0.32 
C) 477 
D) 1.01 
E) 0.50

Question 15

Calculate the intensity level in dB of a sound wave that has an intensity of 15 × 10−4 W/m2.

Accepted Answer

A) 20 
B) 200 
C) 92 
D) 9 
E) 10 
A) 20 
B) 200 
C) 92 
D) 9 
E) 10

Question 16

A point source emits sound with a power output of 100 watts.What is the intensity (in W/m2)at a distance of 10.0 m from the source?

Accepted Answer

A) 7.96 × 10−2 
B) 7.96 × 10−1 
C) 7.96 × 100 
D) 7.96 × 101 
E) 7.96 × 10−3 
A) 7.96 × 10−2 
B) 7.96 × 10−1 
C) 7.96 × 100 
D) 7.96 × 101 
E) 7.96 × 10−3

Question 17

A car moving at 36 m/s passes a stationary police car whose siren has a frequency of 500 hz.What is the change in the frequency (in Hz)heard by an observer in the moving car as he passes the police car? (The speed of sound in air is 343 m/s. )

Accepted Answer

A) 416 
B) 208 
C) 105 
D) 52 
E) 552 
A) 416 
B) 208 
C) 105 
D) 52 
E) 552

Question 18

A point source emits sound waves with a power output of 100 watts.What is the sound level (in dB)at a distance of 10 m?

Accepted Answer

A) 139 
B) 119 
C) 129 
D) 109 
E) 10 
A) 139 
B) 119 
C) 129 
D) 109 
E) 10

Question 19

A stone is thrown into a quiet pool of water.With no fluid friction,the amplitude of the waves falls off with distance r from the impact point as

Accepted Answer

A) 1/r3 
B) 1/r2 
C) 1/r3/2 
D) 1/r1/2 
E) 1/r 
A) 1/r3 
B) 1/r2 
C) 1/r3/2 
D) 1/r1/2 
E) 1/r

Question 20

A microphone in the ocean is sensitive to the sounds emitted by porpoises.To produce a usable signal,sound waves striking the microphone must have an intensity of 1.02 × 10−11 W/m2.If porpoises emit sounds with a power of 0.049 9 W,how far away can a porpoise be and still be heard? Disregard absorption of sound waves by the water.

Accepted Answer

Exam 17: Sound Waves

A spherical wave has the form ) The velocity of the wave (in m/s)is

While you are sounding a tone on a toy whistle,you notice a friend running toward you.If you want her to hear the same frequency that you hear even though she is approaching,you must

A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction.If the frequency of the siren is 500 Hz relative to the police car,what is the frequency heard by an observer in the truck after the police car passes the truck? (The speed of sound in air is 343 m/s. )

By what factor is the intensity of sound at a rock concert louder than that of a whisper when the two intensity levels are 120 dB and 20 dB respectively?

A person standing in the street is unaware of a bird dropping that is falling from a point directly above him with increasing velocity.If the dropping were producing sound of a fixed frequency,as it approaches the person would hear the sound

A sculptor strikes a piece of marble with a hammer.Find the speed of sound through the marble (in km/s).(The Young's modulus is 50 × 109 N/m2 and its density is 2.7 × 103 kg/m3. )

A spherical wave has the form ) The wavelength of the wave is

To decrease the intensity of the sound you are hearing from your speaker system by a factor of 36,you can

When a workman strikes a steel pipeline with a hammer,he generates both longitudinal and transverse waves.The two types of reflected waves return 2.4 s apart.How far away is the reflection point? (For steel,vL = 6.2 km/s,vT = 3.2 km/s)

An airplane traveling at half the speed of sound emits sound at a frequency of 5 000 Hz.At what frequency does a stationary listener hear the sound as the plane approaches,and after it passes by? Assume the airplane is not flying very high.

A source of sound waves is placed at the center of a very large sound-reflecting wall.The source emits 0.500 W of power.Two meters from the source the intensity in W/m2 is

The variation in the pressure of helium gas,measured from its equilibrium value,is given by ΔP = 2.9 × 10−5 cos (6.20x − 3 000t)where x and t have units m and s,and ΔP is measured in N/m2.Determine the wavelength (in m)of the wave.

Calculate the intensity level in dB of a sound wave that has an intensity of 15 × 10−4 W/m2.

A point source emits sound with a power output of 100 watts.What is the intensity (in W/m2)at a distance of 10.0 m from the source?

A car moving at 36 m/s passes a stationary police car whose siren has a frequency of 500 hz.What is the change in the frequency (in Hz)heard by an observer in the moving car as he passes the police car? (The speed of sound in air is 343 m/s. )

A point source emits sound waves with a power output of 100 watts.What is the sound level (in dB)at a distance of 10 m?

A stone is thrown into a quiet pool of water.With no fluid friction,the amplitude of the waves falls off with distance r from the impact point as

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A sculptor strikes a piece of marble with a hammer.Find the speed of sound through the marble (in km/s).(The Young's modulus is 50 × 10⁹ N/m² and its density is 2.7 × 10³ kg/m³. )

When a workman strikes a steel pipeline with a hammer,he generates both longitudinal and transverse waves.The two types of reflected waves return 2.4 s apart.How far away is the reflection point? (For steel,v_L = 6.2 km/s,v_T = 3.2 km/s)

A source of sound waves is placed at the center of a very large sound-reflecting wall.The source emits 0.500 W of power.Two meters from the source the intensity in W/m² is

The variation in the pressure of helium gas,measured from its equilibrium value,is given by ΔP = 2.9 × 10−⁵ cos (6.20x − 3 000t)where x and t have units m and s,and ΔP is measured in N/m².Determine the wavelength (in m)of the wave.

Calculate the intensity level in dB of a sound wave that has an intensity of 15 × 10−⁴ W/m².

A point source emits sound with a power output of 100 watts.What is the intensity (in W/m²)at a distance of 10.0 m from the source?