Alternative Methods for the Measurement of Panel Transmission Loss under Diffuse Acoustic Field Excitation

Three different approaches are described that aim at providing alternative transmission loss measurements to standards, either using a classical coupled room arrangement or a different laboratory installation.The first one consists in reproducing a random excitation at a panel surface using a synthetic array approach, needing only a single monopole source in hemi-anechoic conditions. This approach removes the need of a reverberant room to generate a diffuse acoustic field excitation, and allows estimating the panel behaviour under other random excitations such as a turbulent boundary layer. The two others possibilities describes transmission loss estimations in a standard reverberant-anechoic rooms arrangement, but using 'single quantity' measurements. The transmission loss is first derived using sound intensity measurements only, performed as an insertion loss test (radiated and incident sound intensity are measured when a panel is installed or not). The transmission loss is then derived using vibration measurements only. The virtual fields method allows identifying the parietal pressure field exciting the panel and estimating the corresponding incident acoustic power, while the radiated acoustic power is calculated using the radiation resistance matrix method.For the three approaches, results for a small aluminium panel and a large composite panel are provided, illustrating their respective potentials.