Fast frequency sweep method for indirect boundary element models arising in acoustics

This paper presents an efficient approach for computing frequency sweeps with fine increments of acoustic systems described by the variational indirect boundary element method. The matrices arising from such boundary element discretizations are fully populated and their assembly is computationally demanding as it involves the calculation of double surface integrals for each system matrix entry. Therefore, the two operations performed when computing the response at one frequency, namely assembling the system matrix and solving the associated linear system, may be of the same order of magnitude in terms of the required computational time. The proposed fast frequency sweep approach accelerates both operations. First, it avoids forming the system matrices for each individual frequency. Matrices are only assembled at a few master frequencies, while for the rest, interpolation is used on scaled quantities determined at the master frequencies. Second, it avoids solving a dense linear system at each frequency. Padé approximants constructed via the well-conditioned asymptotic waveform evaluation algorithm are used to extrapolate the response around expansion frequencies using derivative information. The proposed method was tested on an exterior acoustics application representing an academic test case, as well as on an interior/exterior application representing an industrial test case.