Posted by **Anisha** on Thursday, March 10, 2011 at 4:56am.

A loud speaker emits energy in all directions at a rate of 2.75 J/s . What is the intensity level at a distance of 25 m?

- Physics -
**drwls**, Thursday, March 10, 2011 at 7:00am
Divide the total power emitted (2.75 W) by the area of the sphere at that distance, 4*pi*R^2

With R in meters, that will give you the sound intensity in W/m^2 Usually designated by I) . I get I = 3.5*10^-4 W/m^2

There is a formula for converting that to decibels. I get 85 dB

dB = 10 log(10) I/10^-12

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