LOSS FACTORS OF COMPOSITE HONEYCOMB SANDWICH PANELS

Abstract

This paper investigates the sound transmission through foam-filled honeycomb sandwich panels, experimentally and analytically. An analytical model based on statistical energy analysis (SEA) is developed in detail for a honeycomb sandwich panel. By using the SEA method, the sound transmission loss (STL) of honeycomb sandwich panels is described theoretically and a closed-form expression for the STL is presented. The resulting expression yields accurate predictions of transmission loss. The validity of the theoretical result is verified by implementation a comparison with experimental measurement. For this purpose, an experimental set-up was constructed for measuring the sound transmission loss. The set-up consisted of two reverberation chambers, a foam-filled honeycomb sandwich panel and a Brüel & Kjær intensity probe. The sound intensity method with the so-called direct approach was used to measure the transmission loss. Comparisons of the experimental and analytical results show good agreement in the medium and high frequency regions and particularly at the critical frequency of the panel. The critical frequency is estimated by the proposed SEA model with less than 1% error. The reported experimental results can also be used as reference data for further analytical and numerical studies. Based on the SEA theory developed, the effect of design parameters such as the thickness of the face and core layers, the internal loss factor of the sandwich panel and the shear modulus of the core layer on the sound transmission was studied.