This research is on the development of sensors for acoustic detection of low energy deposition in ultra-cold silicon crystals. The investigation will focus on possible methods for the detection of the phonons (sound quanta) produced when energy is absorbed in the crystal. The distribution of these phonons at the crystal surface yields information on the location and amount of energy deposit. If successfully developed, the acoustic sensors and associated silicon crystals could be used to detect neutrinos and other neutral, weakly interacting particles. This would allow sensitive tests of the energetics of the sun, and the possible existence of "dark matter" in the universe.