Benchmark for experimentation of acoustic transmission loss applied to helicopter trim panels

The acoustic Transmission Loss (TL) of a vibrating structure, like a sample of helicopter trim panel, is generally measured in a laboratory set-up within controlled conditions. It represents the ratio between the incident acoustic power and the acoustic power radiated by the panel. To estimate its vibro-acoustic behaviour, it is essential to know precisely the nature of incident pressure field and to distinguish the influence of panel size and boundary conditions. Moreover, the relevance of the outputs depends on the experimental surroundings and instrumentation. The aim of this paper is to present an experimental benchmark study involving different laboratories and operating processes (in laboratory or "in situ ") of "Helicopter GARTEUR (Group for Aeronautical Research and Technology in Europe) Action Group AG20" and relative to the measurement of TL applied to reference trim panels.