When solving transient wave problems it is recommended to use a fixed time stepping in the solver (this is the manual option in the solver settings). In general there is no point in using an automatic time-step control which can be provided by the time-dependent solver. The tolerances in the automatic error control are difficult to tune in wave problems when there is weak but important high-frequency content. It is recommended to use the suggestion generated when the Fixed (preferred) method is chosen (the default) in the Transient Solver Settings section. The internal time step of the solver that is generated, when the Maximal frequency to resolve is set, will in most cases produce a solver that is adequate. It is assuming that the user has generated a mesh that properly resolves the same maximal frequency (minimal wavelength).