Improvement of the sound transmission loss of panels by means of acoustically tuned resonators

When a panel is excited, either structurally or acoustically, sound is radiated from the panel. Previous research by the author has shown that tuned acoustic tube resonators can be used to reduce the radiated sound. A one-dimensional analytical model model was validated by experiments in an impedance tube and good agreement was found between model and measurements. In this paper, the model is extended to describe the sound transmitted through a panel with acoustic resonators. Two different configurations are examined: panels with tubes and perforated sandwich panels. To verify whether the one-dimensional analytical models give a good prediction of the sound transmission loss, panels of both configurations were tested. Sound transmission loss measurements were performed by means of the sound intensitymethod (ISO 15186-1). The measurements showed that the resonators indeed increased the transmission loss compared with the mass law, in the frequency range for which the resonators were tuned. However, the increase was not as large as predicted by the onedimensional model. Resonators can be applied for various structural parts of an aircraft through which the transmission of sound has to be reduced. The research is performed as part of the EU project FACE (Friendly Aircraft Cabin Environment).