  Total absorption, defined as the net flux of energy out of a bounded region
averaged over one cycle for time harmonic motion, must be non-negative when
there are no sources of energy within the region. This passivity condition
places constraints on the non-dimensional absorption coefficients of
longitudinal and transverse waves, $\gamma_L$ and $\gamma_T$, in isotropic
linearly viscoelastic materials. Typically, $\gamma_L, \, \gamma_T$ are small,
in which case the constraints imply that coefficients of attenuation per unit
length, $\alpha_L$, $\alpha_T$, must satisfy the inequality
${\alpha_L}/{\alpha_T} \ge { 4c_{T}^3} / { 3c_{L}^3}$ where $c_L$, $c_T$ are
the wave speeds. This inequality, which as far as the author is aware, has not
been presented before, provides a relative bound on wave speed in terms of
attenuation, or {\it vice versa}. It also serves as a check on the consistency
of ultrasonic measurements from the literature, with most but not all of the
data considered passing the positive absorption test.
