Question 1

Two loudspeakers are placed facing each other and driven by the same source at 680 Hz.A listener is positioned between the two speakers 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) 0.13 m
B) 0.25 m
C) 0.50 m
D) 1.00 m

Accepted Answer

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Question 2

By what amount does the sound intensity decrease when the distance to the source triples?
A) 9.0 dB
B) 9.5 dB
C) 6.0 dB
D) 3.5 dB

Accepted Answer

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Question 3

A vibrating guitar string emits a tone simultaneously with one from a 500-Hz tuning fork.If a beat frequency of 4 Hz results,what is the frequency of vibration of the string?
A) 2500 Hz
B) 496 Hz
C) 504 Hz
D) Either choice B or C is valid.

Accepted Answer

The beat frequency is the absolute difference between the two frequencies. Therefore, the string could be vibrating at either 496 Hz (500 Hz - 4 Hz) or 504 Hz (500 Hz + 4 Hz).

Question 4

If two adjacent frequencies of an organ pipe closed at one end are 500 Hz and 700 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

Accepted Answer

The correct answer is A.The length of an organ pipe closed at one end is given by:$$L = \frac{\lambda}{4}$$where $\lambda$ is the wavelength of the sound wave.The wavelength of a sound wave is given by:$$\lambda = \frac{v}{f}$$where $v$ is the speed of sound and $f$ is the frequency.The two adjacent frequencies are 500 Hz and 700 Hz. So, the wavelength of the sound wave is:$$\lambda = \frac{340 	ext{ m/s}}{500 	ext{ Hz}} = 0.68 	ext{ m}$$Therefore, the length of the organ pipe is:$$L = \frac{0.68 	ext{ m}}{4} = 0.17 	ext{ m}$$

Question 5

What is the lowest frequency that will resonate in an organ pipe 1.00 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

Accepted Answer

The answer of What is the lowest frequency that will...

Question 6

A tuning fork is sounded above an adjustable length resonating tube (one end closed),which resonates at a length of 0.250 m and again at 0.750 m.What is the frequency of the fork when the speed of sound is taken to be 340 m/s?
A) 340 Hz
B) 680 Hz
C) 1020 Hz
D) 170 Hz

Accepted Answer

The resonating tube with one end closed forms a quarter-wave resonator. The first resonance occurs at 0.250 m (1/4 wavelength) and the second at 0.750 m (3/4 wavelength). The difference between these lengths is 0.500 m, which is half a wavelength. Therefore, the full wavelength is 1.000 m. Using the speed of sound (340 m/s), the frequency is calculated as speed/wavelength = 340 m/s / 1.000 m = 340 Hz.

Question 7

A tuning fork is sounded above an adjustable length resonating tube (one end closed),which resonates at a length of 0.250 m and again at 0.750 m.If the tube length were extended further,at what point will the tuning fork again create a resonance condition?
A) 1.75 m
B) 1.50 m
C) 1.25 m
D) 1.00 m

Accepted Answer

The difference between the first and second resonance conditions is (0.750 m - 0.250 m) = 0.500 m, which represents a half wavelength of the sound wave. Thus, the wavelength of the sound wave is 2(0.500 m) = 1.000 m. To create the next resonance condition, the resonating tube length must be extended by another half wavelength, or 0.500 m. Therefore, the additional length of the tube must be 0.500 m - (0.750 m - 0.250 m) = 0.000 m, or the tube must be at a length of 0.750 m + 0.500 m = 1.250 m. Thus, the correct answer is C) 1.25 m.

Question 8

A sound intensity of 70 dB is observed at a distance d from the source of sound.What sound intensity would be observed at a distance 2d from the source?
A) 68 dB
B) 67 dB
C) 64 dB
D) 62 dB

Accepted Answer

The sound intensity decreases inversely proportional to the square of the distance.
So, if the distance is doubled, the sound intensity will decrease to 1/4th of its original value.
Thus, the new sound intensity would be 64 dB, which is answer choice C.

Question 9

Two loudspeakers are placed facing each other and driven by the same source at 680 Hz.A listener is positioned between the two speakers 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) 0.13 m
B) 0.25 m
C) 0.50 m
D) 1.00 m

Accepted Answer

The answer of Two loudspeakers are placed facing each other...

Question 10

A source of sound has an intensity I₁ and when its sound level is measured at a fixed distance the value found is 70 dB.The source then has its intensity increased to I₂ and when its sound level is measured at the same distance the value found is 96 dB.What is the ratio I₂/I₁? A) 26 B) 400 C) 600 D) 14

Accepted Answer

The change in sound level (in dB) is given by: ΔL = 10 log (I₂/I₁) where I₁ and I₂ are the initial and final intensities respectively. Using this formula, we can set up two equations: 70 = 10 log (I₂/I₁) 96 = 10 log (I₃/I₁) Dividing the two equations, we get: ΔL = 96 - 70 = 26 = 10 log (I₃/I₂) Solving for I₃/I₂, we get: I₃/I₂ = 10^(ΔL/10) = 10^(26/10) = 400 Therefore, the ratio I₂/I₁ is 400. The answer is B.

Question 11

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 321 Hz and 326 Hz,respectively?
A) 323.5 Hz
B) 647 Hz
C) 5 Hz
D) 2.5 Hz

Accepted Answer

The beat frequency is given by the absolute value of the difference between the frequencies of the two forks, which is 326 Hz - 321 Hz = 5 Hz.

Question 12

Two tuning forks sounding together result in a beat frequency of 3 Hz.If the frequency of one of the forks is 512 Hz,what is the frequency of the other?
A) 509 Hz or 515 Hz
B) 105 Hz
C) 518 Hz or 506 Hz
D) 85 Hz

Accepted Answer

The beat frequency is the absolute difference between the frequencies of the two tuning forks. Therefore, the other fork can be either 512 Hz + 3 Hz = 515 Hz or 512 Hz - 3 Hz = 509 Hz.

Question 13

A very loud train whistle has an acoustic power output of 80 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) 88.0 dB C) 92.8 dB D) 95.0 dB

Accepted Answer

First, we need to calculate the sound intensity at a distance of 100 meters:
I = P/4πr² = 80/(4π(100)²) = 2.54 x 10^-6 W/m²

Next, we can find the sound intensity level in dB using the formula:
IL = 10 log(I/I0) where I0 = 10^-12 W/m² (reference intensity)

IL = 10 log (2.54 x 10^-6/10^-12) = 88.0 dB

Therefore, the answer is B, 88.0 dB.

Question 14

What is the next harmonic frequency over the fundamental for an organ pipe 1.50 m in length,closed at one end? The speed of sound in air is 340 m/s.
A) 227 Hz
B) 170 Hz
C) 113 Hz
D) 56.7 Hz

Accepted Answer

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Question 15

A flute behaves like a tube open at both ends.If its length is 70.0 cm,and the speed of sound is 340 m/s,what is its fundamental frequency in Hz?
A) 121 Hz
B) 159 Hz
C) 243 Hz
D) 260 Hz

Accepted Answer

Since the flute is open at both ends, its fundamental frequency can be calculated using the formula f = (v/2L), where f is the frequency, v is the speed of sound, and L is the length of the tube. Substituting the given values, we get f = (340/2*0.70) = 243 Hz. Therefore, the correct answer is C.

Question 16

The intensity level of sound 30 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) 60 m
B) 90 m
C) 300 m
D) 400 m

Accepted Answer

Using the inverse square law for spherical spreading of sound, we have:
I1/I2 = (r2/r1)^2
Where I1 is the initial sound intensity level, I2 is the tolerable sound intensity level, r1 is the initial distance from the source, and r2 is the distance we are trying to find.
Plugging in the given values, we get:
120/100 = (30/r2)^2
Solving for r2, we get:
r2 = 300 m

Question 17

A train station bell gives off a fundamental tone of 1000 Hz as the train approaches the station at a speed of 20.0 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) 1060 Hz
B) 1070 Hz
C) 943 Hz
D) 940 Hz

Accepted Answer

The apparent frequency can be calculated using the Doppler effect formula for sound: f' = f * (v + vo) / (v - vs), where f is the source frequency (1000 Hz), v is the speed of sound (335 m/s), vo is the observer's speed (20 m/s), and vs is the source speed (0 m/s, since the bell is stationary). Plugging in the values, f' = 1000 * (335 + 20) / 335 = 1060 Hz.

Question 18

A phase difference of 480° corresponds to what wavelength difference?
A) 3λ
B) 3λ/2
C) 3λ/4
D) 4λ/3

Accepted Answer

The answer of A phase difference of 480° corresponds to...

Question 19

You stand by the railroad tracks as a train passes by.You hear a 950-Hz frequency when the train approaches,which changes to 820 Hz as it goes away.How fast is the train moving? The speed of sound in air is 340 m/s.
A) 14.0 m/s
B) 20.0 m/s
C) 25.0 m/s
D) 37.8 m/s

Accepted Answer

The Doppler effect formula for frequency change is used: $ f' = f \frac{v + v_0}{v - v_s} $ for approaching and $ f' = f \frac{v - v_0}{v + v_s} $ for receding. Solving these equations with given frequencies and speed of sound gives the train speed as 25.0 m/s.

Question 20

A 2.00-m long organ pipe is open at one end and closed at the other.Its fundamental tone has wavelength:
A) 8.00 m.
B) 4.00 m.
C) 2.00 m.
D) 1.00 m.

Accepted Answer

The answer of A 2.00-m long organ pipe is open...

Quiz 13: Vibrations and Waves: Part A

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

A vibrating guitar string emits a tone simultaneously with one from a 500-Hz tuning fork.If a beat frequency of 4 Hz results,what is the frequency of vibration of the string?

If two adjacent frequencies of an organ pipe closed at one end are 500 Hz and 700 Hz,what is the length of the organ pipe? (v_sound = 340 m/s)

What is the lowest frequency that will resonate in an organ pipe 1.00 m in length,closed at one end? The speed of sound in air is 340 m/s.

A tuning fork is sounded above an adjustable length resonating tube (one end closed) ,which resonates at a length of 0.250 m and again at 0.750 m.What is the frequency of the fork when the speed of sound is taken to be 340 m/s?

A tuning fork is sounded above an adjustable length resonating tube (one end closed) ,which resonates at a length of 0.250 m and again at 0.750 m.If the tube length were extended further,at what point will the tuning fork again create a resonance condition?

A sound intensity of 70 dB is observed at a distance d from the source of sound.What sound intensity would be observed at a distance 2d from the source?

A source of sound has an intensity I₁ and when its sound level is measured at a fixed distance the value found is 70 dB.The source then has its intensity increased to I₂ and when its sound level is measured at the same distance the value found is 96 dB.What is the ratio I₂/I₁?

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 321 Hz and 326 Hz,respectively?

Two tuning forks sounding together result in a beat frequency of 3 Hz.If the frequency of one of the forks is 512 Hz,what is the frequency of the other?

A very loud train whistle has an acoustic power output of 80 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)

What is the next harmonic frequency over the fundamental for an organ pipe 1.50 m in length,closed at one end? The speed of sound in air is 340 m/s.

A flute behaves like a tube open at both ends.If its length is 70.0 cm,and the speed of sound is 340 m/s,what is its fundamental frequency in Hz?

The intensity level of sound 30 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 train station bell gives off a fundamental tone of 1000 Hz as the train approaches the station at a speed of 20.0 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 phase difference of 480° corresponds to what wavelength difference?

You stand by the railroad tracks as a train passes by.You hear a 950-Hz frequency when the train approaches,which changes to 820 Hz as it goes away.How fast is the train moving? The speed of sound in air is 340 m/s.

A 2.00-m long organ pipe is open at one end and closed at the other.Its fundamental tone has wavelength: