Sound Field Synthesis by Synthetic Array (SFS-SA) for Diffuse Field or TBL Structural Excitation

Diffuse field or TBL excitation of vehicles are of huge interest in automotive industry, for such excitation reveberent rooms of wind tunnels are necessary, this means high cost experiments. The idea of sound field synthesis to create the acoustic effect corresponding to diffuse field or TBL excitation is of major interest to reduce drastically the cost of experiments. Originally techniques based on Loud speakers antenna [], [], were used. However, a major difficulty appeared due to driving simultaneously a huge number of Loud speakers. To avoid this difficulty a new technique based on Synthetic antenna was proposed in reference [] , instead of an array of loud speakers , just one loud speaker is used for scanning the surface where the acoustic field excite the structure. A post processing based on plane wave decomposition, is then applied to collected data in order to get the response of the structure or the sound transmission through the structure. Different post processing can be applied to get the vibro-acoustics response of structural component due to diffuse field or plane wave excitation or TBL excitation using Corcos, Chase or others models. The theoretical background is first presented in particular the post processing technique and the scanning criteria. In a second part examples of application are shown for diffuse field excitation. The case of TBL excitation is more complicated to handle because the correlation length is much smaller than for plane wave or diffuse field excitation, leading to a smaller mesh for the scanning operation. In addition of avoiding costly experimental techniques the method permits to apply the acoustic field on a part of the car , if people is interested in the sound transmission through the wind shield just apply the synthetized acoustic field to it.