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 11m above the passing cars and measures a maximum intensity level of 80dB . If her new home is 2.4km from the freeway, what's the intensity level there? Assume no decrease due to absorption by air, trees, or other objects. Compare your result with a quiet whisper, 20dB . Thank you!

Explanation / Answer

so at 11m she measures 80 db we use that dB = 10 log(I/I0) 80=10 log(I/I0) I0=10^(-12) 10^8 = I/I0 I = 10^(-4) P = I*4 pir^2 = 10^(-4)*4*pi*11^2 the intensity at her house I =P/4pir^2 = 10^(-4)*11^2/(2400)^2 plug into dB equation dB = 10 log(10^(-4)*11^2/(2400)^2/(10^(-12))=33.22 dB so louder than a quiet whisper

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