Having grown tired of hearing loud music from passing cars at 3 am and the boist

Question

Having grown tired of hearing loud music from passing cars at 3 am and the boisterous yelling of bar patrons at closing, a professor buys a new home in a quiet neighborhood. She is, however, concerned about noise from freeway traffic. Using a sound intensity level meter,she stands at an overpass 7.0m above the passing cars and measures a maximum intensity level of 78dB .

Part A

If her new home is 3.0km from the freeway, what's the intensity level there? Assume no decrease due to absorption by air, trees, or other objects.

SIL2 =

Part B

Compare your result with a quiet whisper, 20 dB.

?SIL =

Explanation / Answer

a)

I2/I1 = d1^2 / d2^2

=> 10log(I2/I1) = 20log(d1/d2)

=> 10log(I2/I0) - 10log(I1/I0) = 20log(d1/d2)

=> 10log(I2/I0) - 78 = 20log(7/3000)

=> 10log(I2/I0) = 25.36 dB

B)

?SIL = 25.36 dB - 20 dB

= 5.36 dB

so,

it is 5.36 dB louder than whisper

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