  This article investigates residual a posteriori error estimates and adaptive
mesh refinements for time-dependent boundary element methods for the wave
equation. We obtain reliable estimates for Dirichlet and acoustic boundary
conditions which hold for a large class of discretizations. Efficiency of the
error estimate is shown for a natural discretization of low order. Numerical
examples confirm the theoretical results. The resulting adaptive mesh
refinement procedures in 3d recover the adaptive convergence rates known for
elliptic problems.
