On the in situ estimation of surface acoustic impedance in interiors of arbitrary shape by acoustical inverse methods

Abstract

A method for in situ estimation of the acoustic impedance of surfaces in interiors is introduced in this paper. The key difference with traditional in situ measurement techniques is the use of an inverse acoustic boundary framework which allows us to overcome some geometry constraints from previous methods (such as the planar-surface requirement and placement of microphone arrays). Furthermore, estimation of the acoustic impedance of not only one but all the surfaces is possible provided that local reaction is the predominant effect, and the following parameters are known: geometry of the surfaces, sound pressure at a number of arbitrary points in the interior field and the strength of the sound source. The estimation of the acoustic impedance at each surface is achieved by the solution of an optimization problem formulated from the linear equations of the boundary element method (BEM) applied to the discretized interior boundaries of an interior space. Previous work on similar methods have reported examples with numerical simulations. The work in this paper goes further and numerical examples together with results obtained with experimental data are presented.