Experimental study on the effect of specimen size on sound insulation of precast panels

This study was carried out to investigate on the effect of specimen size on evaluation of sound insulation of relatively heavyweight precast panels. The size of small specimen was determined by considering the first resonance frequency to be generated just below 100 Hz. The experimental results of single and double walls show that the behaviour of sound reduction index by the variation of specimen size is markedly changed below the critical frequency and in the coincidence region. For example, the sound reduction index of small specimens is decreased below the critical frequency and does not follow the mass law. In the coincidence region, on the other hand, there were some increases of the sound reduction index for small specimens due to the variation of boundary condition. These results indicate that the resonant transmission and boundary condition which are usually neglected in the prediction of sound insulation should be considered as important prediction variables especially for the small specimen of relatively heavyweight walls.