  Diffusing wave spectroscopy (DWS) can be employed as an optical rheology tool
with numerous applications for studying the structure, dynamics and linear
viscoelastic properties of complex fluids, foams, glasses and gels. To carry
out DWS measurements, one first needs to quantify the static optical properties
of the sample under investigation, i.e. the transport mean free path $l^\ast$
and the absorption length $l_a$. In the absence of absorption this can be done
by comparing the diffuse optical transmission to a calibration sample whose
$l^\ast$ is known. Performing this comparison however is cumbersome, time
consuming and prone to mistakes by the operator. Moreover, already weak
absorption can lead to significant errors. In this paper, we demonstrate the
implementation of an automatized approach, based on which the DWS measurement
procedure can be simplified significantly. By comparison with a comprehensive
set of calibration measurements we cover the entire parameter space relating
measured count rates (CR$_t$, CR$_b$) to ($l^\ast$, $l_a$). Based on this
approach we can determine $l^\ast$ and $l_a$ of an unknown sample accurately
thus making the additional measurement of a calibration sample obsolete. We
illustrate the use of this approach by monitoring the coarsening of a
commercially available shaving foam with DWS.
