Air Absorption

From Moorer 1979:

$$I(r) = I_0 e^{-r/\tau_r}$$

where

$$\begin{eqnarray*} I_0 &=& \hbox{intensity at the source}\\ I(r) &=& \hbox{inten... ...on frequency, temperature, humidity}\\ & & \hbox{and pressure)} \end{eqnarray*}$$

Relative	Frequency in Hz
Humidity	1000	2000	3000	4000
40	5.6	16	30	105
50	5.6	12	26	90
60	5.6	12	24	73
70	5.6	12	22	63

$\parbox{5in}{\emph{Attenuation} in dB per kilometer at 20\mbox{${}^{\circ}$}C and standard atmospheric pressure.}$