Acoustic Intensity

Acoustic Intensity may be defined by

$$\zbox{\underline{I} \mathrel{\stackrel{\mathrm{\Delta}}{=}}p \und... ...ox{\large Time}} = \frac{\mbox{\large Power Flux}}{\mbox{\large Area}}\right)$$

where

$$\begin{eqnarray*} p &=& \mbox{acoustic pressure} \quad \left(\frac{\mbox{\large ... ...uad \left(\frac{\mbox{\large Length}}{\mbox{\large Time}}\right) \end{eqnarray*}$$

For a plane traveling wave, we have

$$\zbox{p = R v}$$

where

$$R \mathrel{\stackrel{\mathrm{\Delta}}{=}}\rho c$$

is called the wave impedance of air, and

$$\begin{eqnarray*} c &=& \mbox{sound speed}\\ \rho &=& \mbox{mass density of air... ...tackrel{\mathrm{\Delta}}{=}}& \left\vert\underline{v}\right\vert \end{eqnarray*}$$

Therefore, in a plane wave,

$$\zbox{I = p v = Rv^2 = \frac{p^2}{R}}$$