Fast computation of time-dependent acoustic fields

We present a method for the fast evaluation of time-dependent acoustic fields from complex sources. The technique is based on a fast integration method for the boundary integral arising in a Kirchhoff formulation and requires a small, and roughly constant, computation time to compute a transient signal, at the expense of a pre-processing stage. In our calculations, based on test cases for a single rotor and a counter-rotating open rotor, we find that transient field calculations require an order of magnitude less computational time for the field from an array of~16384 sources, a computational advantage which increases with source number.