Why using complex stimuli for acoustical measurements may be necessary to get physically relevant analysis results.

Abstract

Classical methods for measurements and analysis in Musical Acoustics (and also Acoustics) rely on Fourier transforms, linear excitation superposition assumption, and monochromatic excitation or noise equivalents. It is shown that classical methods using measurements at a single point (input impedance measurement, for instance) may not be physically relevant. Indeed, only a time sampling and related time Fourier transforms are performed while physical phenomena are spatio‐temporal. Even if one considers a monochromatic forward traveling wave excitation, the use of the dispersion relation is not valid in spatio‐temporal or spatio‐frequency parameter space. It is shown that measurements need to be performed using also a spatial mapping to be physically relevant which implies at least Fourier bi‐transforms (plane case). Then, it may be more simple and physically relevant to perform measurements with the whole complex excitation and use a frequency subband analysis tool, with a perceptive frequency subband mapping. Such a tool is described and it is shown that is permits the real‐time switch between listening of partial to total resynthesis for any studied measurement signal, providing great surprises for the physical relevant subband(s) and the perceptive relevant ones. Audio performance will be given.