Inverse Square Law

Sound propagates in three dimensions.
As sound spreads out from a source it gets weaker. This is due to the energy of the sound waves being spread more and more thinly.

Area of a sphere: A_sphere = 4πr²

I = W_source ÷ A_sphere = W_source ÷ 4πr²

I = sound intensity (in W m^-2)
W_source = power of the source (in W)
r = distance from the source (in m)

© Matt Bellingham 2003 – 2006

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