Belgian Building Research Institute
The stringent acoustical requirements imposed by the Belgian standard for dwellings (NBN-S01-400-1 (2008)) present a major challenge for architects. In particular the standard defines strict requirements for the global sound insulation between rooms which is mainly determined by the direct transmission and flanking transmissions in which sound waves produced in one of the rooms excite the flanking structure and generate structural waves which are transmitted through the structure.
BBRI researchers evaluated the incumbent and new prediction formulas over a wide range of surface mass ratios in the case of the old formula, and ratio of characteristic moment impedances in the case of the new formula. The results showed that for in-line and corner transmission in T-junctions, X-junctions and H-junctions the new formula more accurately predicts Kij. This work shows that a best prediction of Kij can be obtained by using the ratio of the characteristic moment-impedances “A” instead of the ratio of surface masses. It seems logical that the attenuation of vibration depends on this new ratio since during a change of direction only moments and angular velocities can participate in energy transmission.