Nicolas Zerbib

Passive and active acoustic properties of a diaphragm at low Mach number: Experimental procedure and numerical simulation

In this paper a low noise flow duct facility that performs a multimodal characterization of the passive and active acoustic properties of obstacles in the aero-acoustic conditions of an automotive air conditioning system is presented. The experimental procedure is made of two steps. In the first one the passive data, i.e. the multimodal scattering matrix, is measured with a multi-sources method. In the second step the outgoing modal pressure spectra radiated upstream and downstream by the flow obstacle interaction source is achieved. A numerical simulation of the experiment based on a 3D-Finite Element Method is developed. A very good agreement between the theoretical and experimental results of the no flow scattering matrix of a diaphragm is found. The effect of the flow on the scattering matrix is shown before performing the measurement of the aero-acoustic source characteristics of the diaphragm.