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Acoustic Intensity

Acoustic intensity may be defined by


$\displaystyle \zbox {\underline{I} \isdefs p \underline{v}}
\quad \left(\frac{\...
...mall Time}}
\eqsp
\frac{\mbox{\small Power Flux}}{\mbox{\small Area}}\right)
$

where
\begin{eqnarray*}
p &=& \mbox{acoustic pressure} \quad \left(\frac{\mbox{\small ...
...ad \left(\frac{\mbox{\small Length}}{\mbox{\small Time}}\right).
\end{eqnarray*}
For a plane traveling wave, we have

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

where

$\displaystyle \zbox {R \isdefs \rho c}
$

is called the wave impedance of air, and
\begin{eqnarray*}
c &=& \mbox{sound speed},\\
\rho &=& \mbox{mass density of ai...
...ume}}\right),\\
v &\isdef & \left\vert\underline{v}\right\vert.
\end{eqnarray*}
Therefore, in a plane wave,

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


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