Catalogue of Vibration Reduction Index Formulas for Heavy Junctions Based on Numerical Simulations

The vibration reduction index (K_ij ) is a key parameter in the prediction of flanking transmissions according to the EN-12354 standard. Formulas for the evaluation of K_ij in L, T and X junctions that depend on the mass ratio are available in the Annex E. Junctions of straight elements with different thickness or thin elastic layers are also included. However, other junction types that are important for building industry are not considered: H-shaped junctions, L or T junctions not forming a right angle, asymmetrical T-junctions, X-junctions where only one of the parts is different (thickness or material) from the other two/three. In the current research, expressions for these non-covered junctions are provided. They are obtained by means of numerical simulations based on the spectral finite element method. K_ij is predicted for a large population of junctions, considering usual thicknesses and heavy material combinations (no lightweight frame systems have been considered). Statistical analysis is carried out to obtain relatively simple formulae that could be used in acoustic design projects without the need for time-consuming computations with finite element software.