Within the WKB (Wentzel‐Kremers‐Brillouin) or geometrical optics approximation, a wave packet can be taken to be made up of phonons transporting energy, momentum, and angular momentum. The energy‐momentum tensor formalism provides single generalized expressions for the conservation of these quantities and for the exchange of energy and momentum between the wave packet and the background medium. The formalism also leads to a clearer interpretation of wave energy and wave momentum; in many problems of geophysical interest, it is necessary to introduce modified concepts of the momentum density of a p