Multi-channel spectral analysis of multi-pass acquisition measurements

Conditioned spectral analysis (CSA) and virtual source analysis (VSA) are two techniques currently used nowadays to post-treat measurements on multiple input multiple output (MIMO) systems. Those techniques are based on the estimation of cross-spectral quantities between outputs and the so-called “references”. In some measurement situations, all outputs cannot be acquired simultaneously, several measurement passes are necessary (using a scanning system, a robot or a laser vibrometer). An approach is proposed in this paper to adapt CSA and VSA to MIMO systems requiring a multi-pass acquisition. The approach is based on the average over all passes of a set of reference channels, and on the correction of cross-spectral quantities by using transfer functions and averaged reference spectra. An academic experiment is finally realized to illustrate the proposed approach.