  We present a model to calculate heat signal shapes from low temperature
bolometer attached to a crystal. This model is based on the elementary acoustic
wave theory at low temperature, and has been developed using modern Monte Carlo
techniques. Physical processes in phonon propagation, such as transmission,
scattering and reflection are considered. Using our model, the calculated time
dependence of signal agrees with real experimental data. This model has
applications in low temperature rare event particle detectors for dark matter
and neutrinos.
