Sound Intensity in Relation to Distance Formula

Equation for calculate sound intensity in relation to distance is,

$$I_{\mathrm{<mn>2</mn>}}=I_{\mathrm{<mn>1</mn>}}·\frac{{r_{\mathrm{<mn>1</mn>}}}^2}{{r_{\mathrm{<mn>2</mn>}}}^2}$$

where,
I₁ = The sound intensity at close distance r₁
r₁ = The close distance from the centre of the source
r₂ = The far distance from the centre of the source
I₂ = The sound intensity at far distance r₂