How Do You Calculate Decibel Intensity at a Distance in Spherical Waves?

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SUMMARY

The discussion focuses on calculating the decibel intensity of a spherical wave at a distance of 100 meters from a source with an initial intensity of 8.0 W/m² at 1.0 meter. The relevant equation used is β = 10 log(I1/I0), where I0 is the reference intensity of 10^-12 W/m². The intensity of spherical waves decreases with the square of the distance, and the participants clarify the distinction between relative and absolute intensity in decibel measurements.

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Homework Statement


The intensity of a certain spherical wave is 8.0 W/m^2 at a distance of 1.0 m from the source. If the medium is isotropic and nonabsorbing, calculate the decibel intensity 100m from the source.

Homework Equations


β=10ln(I1/I0)

The Attempt at a Solution


I know how to use these equations... And to find the original dB level i use
β=(10dB)ln(8.0/10^-12)

Im just not sure what to do to find intensity 100m away?
 
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What do you mean with "original dB level"?

How does intensity depend on distance for spherical waves without absorption?
 
"Decibel" is very confusing because the term is used both for relative and absolute intensities. As far as I am aware, the unit dB always denotes (or should always denote) a relative intensity. If an absolute intensity is intended then it should be qualified to indicate the reference level, like dBm or dBmW.
Where does your 10-12 come from?
 

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