Question 1

In the afternoon,the decibel level of a busy freeway is 85 dB with 90 cars passing a given point every minute.Late at night,the traffic flow is only 8 cars per minute.What is the late-night decibel level?

Accepted Answer

The decibel level is proportional to the logarithm of the intensity. Assuming each passing car makes the same noise, the number of cars passing a given point is directly proportional to the intensity of the sound. Thus, we can use the formula I1/I2 = (dB2 - dB1) / 10, where I1 and I2 are the intensities of the sound, and dB1 and dB2 are the corresponding decibel levels.

Let's set up the equation for the two scenarios given:

I1 / I2 = 90 / 8   (ratio of cars passing)

85 / dB2 = log(90 / 8) / log 10   (solve for dB2)

dB2 = 74 dB

Therefore, the answer is D, 74 dB.

Question 2

If I₀ = 10−¹² W/m² is the threshold of hearing,a sound with intensity I₁ = 10−¹¹ W/m² will give a certain decibel level.Suppose a new sound has an intensity I₂ = 2I₁²/I₀.What is the new decibel level?

Accepted Answer

The sound intensity level (SIL) in decibels (dB) is given by SIL = 10log(I/I_0), where I is the sound intensity and I_0 is the threshold of hearing 10^(-12) W/m^2.

The initial sound has an intensity of I = 10^(-11) W/m^2, so its SIL is SIL1 = 10log(10^(-11)/10^(-12)) = 110 dB.

The new sound has an intensity of I' = 2I/10^(-12) = 2x10^(-11) W/m^2, so its SIL is SIL2 = 10log(2x10^(-11)/10^(-12)) = 120 dB.

Therefore, the change in decibel level is SIL2 - SIL1 = 120 dB - 110 dB = 10 dB, which is equivalent to a perceived doubling of loudness.

The closest answer choice is B, 23 dB, which is incorrect. Therefore, there is no exact match, and the closest answer is B.

Question 3

Tripling the distance between sound source and a listener will change the intensity,as detected by the listener,by what factor?

Accepted Answer

According to the inverse square law, the intensity of sound decreases with the square of the distance. Tripling the distance would result in nine times the original distance, so the intensity would decrease by a factor of 9. Therefore, the answer is A.

Question 4

What sound level change corresponds to a factor of two change in intensity?

Accepted Answer

The formula to calculate the change in decibel level with respect to the intensity is given by ΔL=10log10(I2/I1). 
If the intensity changes by a factor of 2, then I2/I1=2, and the above formula becomes ΔL=10log10(2)=10*0.301=3.01 dB, which can be approximated as 3.0 dB. Therefore, the correct answer is option C.

Question 5

If one-third of the members of a symphony orchestra are absent because of head colds,thus reducing the overall intensity of sound by 33%,what will be the reduction in the decibel level?

Accepted Answer

The decibel level is calculated using the formula 10 * log10(I1/I0), where I1 is the final intensity and I0 is the initial intensity. A 33% reduction in intensity means the final intensity is 67% of the initial, or I1/I0 = 0.67. Plugging this into the formula gives a reduction of approximately 1.8 dB.

Question 6

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?

Accepted Answer

Sound intensity decreases with distance from the source according to the inverse square law. This means that at a distance of 2d, the sound intensity will be reduced to 1/4 (or 6 dB lower) of the original intensity at distance d.

Using the formula I2 = I1/(d2/d1)², where I1 is the initial intensity, d1 is the initial distance, I2 is the final intensity, and d2 is the final distance, we can calculate the new sound intensity:

I2 = 70 dB / (2/1)²
I2 = 70 dB / 4
I2 = 17.5 dB

Taking into account that the decrease in intensity is 6 dB, we can subtract this from the initial intensity of 70 dB to obtain:

I2 = 70 dB - 6 dB
I2 = 64 dB

Therefore, the new sound intensity observed at a distance of 2d from the source is 64 dB.

Question 7

If the distance between a point sound source and a dB detector is increased by a factor of 8,what will be the reduction in intensity level?

Accepted Answer

The intensity level in decibels (dB) is calculated using the formula $L = 10 \log \left(\frac{I}{I_0}\right)$, where $I$ is the intensity of the sound and $I_0$ is the reference intensity. The intensity of sound follows an inverse square law with distance, meaning if the distance is increased by a factor of 8, the intensity decreases by a factor of $8^2 = 64$. Using the formula for change in decibels, $\Delta L = 10 \log \left(\frac{1}{64}\right) = 10 \log \left(\frac{1}{2^6}\right) = 10 \times -6 \log(2) \approx -18 dB$, indicating an 18 dB reduction in intensity level.

Question 8

What is the intensity of a sound with a measured intensity level of 85 dB? (I₀ = 10−¹² W/m²)

Accepted Answer

The answer of What is the intensity of a sound...

Question 9

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

Accepted Answer

The decrease in sound intensity is related to the inverse square of the distance. When the distance doubles, the intensity decreases by a factor of four (2^2). Each factor of four reduction corresponds to a decrease of 6 dB, so when the distance doubles, the intensity decreases by 6 dB. Therefore, the correct answer is D.

Question 10

Quadrupling the power output from a speaker emitting a single frequency will result in what increase in loudness?

Accepted Answer

The increase in loudness (measured in dB) when the power output is increased 4 times is given by:

20log10(4) = 6.02 dB

Therefore, the correct answer is option C) 6.0 dB.

Question 11

If the intensity of a sound is increased by a factor of 100,how is the decibel level changed? The new decibel level will be:

Accepted Answer

The decibel (dB) scale is logarithmic, meaning that a 10-fold increase in intensity corresponds to an increase of 10 dB. Therefore, a 100-fold increase in intensity (i.e., 10^2) corresponds to an increase of 20 dB (i.e., 10 x 2). Thus, the new decibel level will be 20 units greater. Therefore, the correct answer is option D.

Question 12

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?

Accepted Answer

The difference in sound level between the two measurements is 26 dB (96 dB - 70 dB). According to the equation for sound level, this corresponds to a factor of 10^(26/10) = 398.107. Therefore, the ratio of the new intensity to the original intensity is approximately 398.107, which is closest to answer choice B) 400.

Question 13

What is the intensity of sound from a band with a sound level of 129 dB? (I₀ = 10−¹² W/m²)

Accepted Answer

The intensity of sound (I) in watts per square meter (W/m^2) can be calculated using the formula I = 10^(sound level in dB / 10) * 10^-12. For a sound level of 129 dB, the calculation is I = 10^(129/10) * 10^-12 = 7.94 W/m^2.

Question 14

What is the intensity level of a sound with intensity of 6.0 × 10−¹⁰ W/m²? ( I₀ = 10−¹² W/m²)

Accepted Answer

The equation for finding the sound intensity level (SIL) in decibels (dB) is:

SIL = 10 log⁡(I/I_0)

where I_0 is the threshold of human hearing, which is 10^-12 W/m^2.

Substituting the given intensity value in the equation, we get:

SIL = 10 log⁡(6.0 × 10^-11 W/m^2 ÷ 10^-12 W/m^2)

SIL = 10 log⁡(6.0 × 10^1)

SIL = 10 × 1.78

SIL = 17.8 dB

Therefore, the closest answer choice is D) 28 dB, which is closest to the calculated SIL.

Question 15

A very loud train whistle has an acoustic power output of 100 W.If the sound energy spreads out spherically,what is the intensity level in dB at a distance of 89.0 meters from the train? (I₀ = 10−¹² W/m²)

Accepted Answer

The answer of A very loud train whistle has an...

Question 16

A speaker designed to emit spherical sound waves is producing a sound intensity of 8 W/m² at a distance of 1 m from the speaker.What would be the intensity of this sound at a distance of 2 m from the speaker?

Accepted Answer

The answer of A speaker designed to emit spherical sound...

Question 17

As a train starts from rest and then accelerates down the track,coming toward me faster and faster,the speed of the sound waves coming toward me will be

Accepted Answer

The speed of sound waves in air is determined by the properties of the air (temperature, humidity, etc.) and not by the speed of the source of the sound. Therefore, even if the train accelerates towards you, the speed of the sound waves coming towards you remains equal to the normal speed of sound in air.

Question 18

An iceberg breaks off from a glacier on the shore of the ocean with a loud cracking sound.the air.A person on a ship hears the sound in the water 4.0 s before hearing the sound in the air.How far away is the ship? The ambient temperature is -5.0S1U1P1$\circ$S1S1P0C.The speed of sound in saltwater is 1 530 m/s.

Accepted Answer

Let's assume the distance between the iceberg and the ship be 'd' meters.

We know that the speed of sound in water is 1 530 m/s and the speed of sound in air at -5°C is approximately 331 m/s.

The time difference between the person hearing the sound in water and air is 4.0 s.

Therefore, we can write:
d/1530 - d/331 = 4

Multiplying through by 1530*331, we get:
d*331 - d*1530 = 4*1530*331
1199d = 2 018 640
d = 1 682.6 ≈ 1 700 m

Hence, the best answer choice is B) 1 700 m.

Question 19

​A common approximation is when the intensity of a sound is doubled,the decibel level increases by 3.The sound level in a particular location is 100 dB.By what approximate factor is the sound intensity increased if the new decibel level of this sound is 106?

Accepted Answer

According to the approximation, a 6 dB increase corresponds to a factor of 4 increase in sound intensity. Therefore, to go from 100 dB to 106 dB, there is a 6 dB increase, which corresponds to a 4-fold increase in sound intensity.

Question 20

Which of the following best describes a sound level of intensity 1 W/m²?

Accepted Answer

A sound level of intensity 1 W/m^2 is extremely loud, far exceeding typical environmental or even industrial noise levels.

Quiz 14: Sound

In the afternoon,the decibel level of a busy freeway is 85 dB with 90 cars passing a given point every minute.Late at night,the traffic flow is only 8 cars per minute.What is the late-night decibel level?

If I₀ = 10−¹² W/m² is the threshold of hearing,a sound with intensity I₁ = 10−¹¹ W/m² will give a certain decibel level.Suppose a new sound has an intensity I₂ = 2I₁²/I₀.What is the new decibel level?

Tripling the distance between sound source and a listener will change the intensity,as detected by the listener,by what factor?

What sound level change corresponds to a factor of two change in intensity?

If one-third of the members of a symphony orchestra are absent because of head colds,thus reducing the overall intensity of sound by 33%,what will be the reduction in the decibel level?

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?

If the distance between a point sound source and a dB detector is increased by a factor of 8,what will be the reduction in intensity level?

What is the intensity of a sound with a measured intensity level of 85 dB? (I₀ = 10−¹² W/m²)

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

Quadrupling the power output from a speaker emitting a single frequency will result in what increase in loudness?

If the intensity of a sound is increased by a factor of 100,how is the decibel level changed? The new decibel level will be:

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?

What is the intensity of sound from a band with a sound level of 129 dB? (I₀ = 10−¹² W/m²)

What is the intensity level of a sound with intensity of 6.0 × 10−¹⁰ W/m²? ( I₀ = 10−¹² W/m²)

A very loud train whistle has an acoustic power output of 100 W.If the sound energy spreads out spherically,what is the intensity level in dB at a distance of 89.0 meters from the train? (I₀ = 10−¹² W/m²)

A speaker designed to emit spherical sound waves is producing a sound intensity of 8 W/m² at a distance of 1 m from the speaker.What would be the intensity of this sound at a distance of 2 m from the speaker?

As a train starts from rest and then accelerates down the track,coming toward me faster and faster,the speed of the sound waves coming toward me will be

An iceberg breaks off from a glacier on the shore of the ocean with a loud cracking sound.the air.A person on a ship hears the sound in the water 4.0 s before hearing the sound in the air.How far away is the ship? The ambient temperature is -5.0^$\circ$C.The speed of sound in saltwater is 1 530 m/s.

A common approximation is when the intensity of a sound is doubled,the decibel level increases by 3.The sound level in a particular location is 100 dB.By what approximate factor is the sound intensity increased if the new decibel level of this sound is 106?

Which of the following best describes a sound level of intensity 1 W/m²?

Quiz 14: Sound

In the afternoon,the decibel level of a busy freeway is 85 dB with 90 cars passing a given point every minute.Late at night,the traffic flow is only 8 cars per minute.What is the late-night decibel level?

If I0 = 10−12 W/m2 is the threshold of hearing,a sound with intensity I1 = 10−11 W/m2 will give a certain decibel level.Suppose a new sound has an intensity I2 = 2I12/I0.What is the new decibel level?

Tripling the distance between sound source and a listener will change the intensity,as detected by the listener,by what factor?

What sound level change corresponds to a factor of two change in intensity?

If one-third of the members of a symphony orchestra are absent because of head colds,thus reducing the overall intensity of sound by 33%,what will be the reduction in the decibel level?

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?

If the distance between a point sound source and a dB detector is increased by a factor of 8,what will be the reduction in intensity level?

What is the intensity of a sound with a measured intensity level of 85 dB? (I0 = 10−12 W/m2)

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

Quadrupling the power output from a speaker emitting a single frequency will result in what increase in loudness?

If the intensity of a sound is increased by a factor of 100,how is the decibel level changed? The new decibel level will be:

A source of sound has an intensity I​1 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 I​2 and when its sound level is measured at the same distance the value found is 96 dB.What is the ratio ​I​2/​I​1?

What is the intensity of sound from a band with a sound level of 129 dB? (I0 = 10−12 W/m2)

What is the intensity level of a sound with intensity of 6.0 × 10−10 W/m2? ( I0 = 10−12 W/m2 )

A very loud train whistle has an acoustic power output of 100 W.If the sound energy spreads out spherically,what is the intensity level in dB at a distance of 89.0 meters from the train? (I0 = 10−12 W/m2)

A speaker designed to emit spherical sound waves is producing a sound intensity of 8 W/m2 at a distance of 1 m from the speaker.What would be the intensity of this sound at a distance of 2 m from the speaker?

As a train starts from rest and then accelerates down the track,coming toward me faster and faster,the speed of the sound waves coming toward me will be

​A common approximation is when the intensity of a sound is doubled,the decibel level increases by 3.The sound level in a particular location is 100 dB.By what approximate factor is the sound intensity increased if the new decibel level of this sound is 106?

Which of the following best describes a sound level of intensity 1 W/m2?

If I₀ = 10−¹² W/m² is the threshold of hearing,a sound with intensity I₁ = 10−¹¹ W/m² will give a certain decibel level.Suppose a new sound has an intensity I₂ = 2I₁²/I₀.What is the new decibel level?

What is the intensity of a sound with a measured intensity level of 85 dB? (I₀ = 10−¹² W/m²)

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?

What is the intensity of sound from a band with a sound level of 129 dB? (I₀ = 10−¹² W/m²)

What is the intensity level of a sound with intensity of 6.0 × 10−¹⁰ W/m²? ( I₀ = 10−¹² W/m²)

A very loud train whistle has an acoustic power output of 100 W.If the sound energy spreads out spherically,what is the intensity level in dB at a distance of 89.0 meters from the train? (I₀ = 10−¹² W/m²)

A speaker designed to emit spherical sound waves is producing a sound intensity of 8 W/m² at a distance of 1 m from the speaker.What would be the intensity of this sound at a distance of 2 m from the speaker?

A common approximation is when the intensity of a sound is doubled,the decibel level increases by 3.The sound level in a particular location is 100 dB.By what approximate factor is the sound intensity increased if the new decibel level of this sound is 106?

Which of the following best describes a sound level of intensity 1 W/m²?