The second coefficient of viscosity (or bulk viscosity) is a parameter that, just as the shear viscosity, is suitable, e.g., for condition monitoring applications. Its measurement is based on the attenuation of bulk acoustic waves in the analyte and is thus based on measurements in the bulk of a liquid rather than a surface layer (as in many shear viscosity sensors). In our contribution, we review the relevant considerations associated with this approach including spurious diffraction and reflections.