  Specific heat measurements of hydrogenated amorphous silicon prepared by
hot-wire chemical vapor deposition show a large density of two-level systems at
low temperature. Annealing at 200 {\deg}C, well below the growth temperature,
does not significantly affect the already-low internal friction or the sound
velocity, but irreversibly reduces the non-Debye specific heat by an order of
magnitude at 2 K, indicating a large reduction of the density of two-level
systems. Comparison of the specific heat to the internal friction suggests that
the two-level systems are uncharacteristically decoupled from acoustic waves,
both before and after annealing. Analysis yields an anomalously low value of
the coupling constant, which increases upon annealing but still remains
anomalously low. The results suggest that the coupling constant value is
lowered by the presence of hydrogen.
