  We propose a new approach towards determining the distribution of mechanical
and acoustic wave energy in complex built-up structures. The technique
interpolates between standard Statistical Energy Analysis (SEA) and full ray
tracing containing both these methods as limiting case. By writing the flow of
ray trajectories in terms of linear phase space operators, it is suggested here
to reformulate ray-tracing algorithms in terms of boundary operators containing
only short ray segments. SEA can now be identified as a low resolution ray
tracing algorithm and typical SEA assumptions can be quantified in terms of the
properties of the ray dynamics. The new technique presented here enhances the
range of applicability of standard SEA considerably by systematically
incorporating dynamical correlations wherever necessary. Some of the
inefficiencies inherent in typical ray tracing methods can be avoided using
only a limited amount of the geometrical ray information. The new dynamical
theory - Dynamical Energy Analysis (DEA) - thus provides a universal approach
towards determining wave energy distributions in complex structures.
