Equations for material absorption in the water column are summarized by Urick[53]. A somewhat standard form due to Thorpe is:
where f is the frequency in kilohertz and 
is in units of
dB/m. Attenuation in sediments is somewhat more complicated and must be
specified directly.
Material absorption is included by adding an imaginary part to the sound
speed so that 
. Typically, the attenuation is
specified in more physical units so it is necessary to perform a
conversion. In the following subsections we present the results for
various cases.