Identification of noise sources by means of inverse finite element method using measured data

Abstract

Identification of noise sources in airplane cabins proves to be difficult particularly at low frequencies. A new approach reconstructs the spatial distribution of sound pressure and particle velocity based on the inverse finite element (FE) method. This procedure requires measurements in the cavity of the cabin. If all sound sources are located on the boundary of the cabin, the equation system resulting from a matching FE model can be resorted in such way that computation of the unknown boundary data is possible, even with distorted measurement data. The method is explained using a simplified 2D laboratory experiment consisting of a flat sound‐hard bounded rectangle with a loudspeaker included in the boundary. A corresponding FE model with given boundary conditions is verified by mapping the sound pressure in the test bed. The inner part of the measurement data is used to compute the boundary values. Regularization methods are applied to find an optimal solution. To prepare a verification of this technique in real world conditions, the sound field in the cavity of an airplane mock‐up (Airbus A340) exited by both an interior and exterior noise source is mapped with a custom‐built microphone array. Taking advantage of the results of the 2D examination, the current status of this verification process is shown.