  The elastic properties of hcp $^4$He samples have been investigated using low
frequency (20 Hz to 20 kHz) high sensitivity sound transducers. In agreement
with the findings of other workers, most samples studied grew very
significantly stiffer at low temperature; Poisson's ratio $\nu$ was observed to
increase from 0.28 below 20 mK to $\sim 0.35$ at 0.7 K. The span of the
variation of $\nu$ varies from sample to sample according to their thermal and
mechanical history. Crystals carefully grown at the melting curve show a
different behavior, the change in $\nu$ taking place at lower $T$ and being
more abrupt.
