Drop a pebble in a pond and the results are predictable: circular waves flow from the point of impact. Hit a point on a crystalline solid, however, and the expanding waves are highly nonspherical; the elasticity of a crystal is anisotropic. This book provides a fresh look at the vibrational properties of crystalline solids, elucidated by new imaging techniques. From the megahertz vibrations of ultrasound to the near-terahertz vibrations associated with heat, the underlying elastic anisotropy of the crystal asserts itself. Phonons are elementary vibrations that affect many properties of solids--thermal, electrical, and magnetic. This text covers the basic theory and experimental observations of phonon propagation in solids. Phonon imaging techniques provide physical insights into such topics as phonon focusing, lattice dynamics, and ultrasound propagation. Scattering of phonons from interfaces, superlattices, defects, and electrons are treated in detail. The book includes many striking and original illustrations.