PREDICTING THE SOUND REDUCTION INDEX OF LAMINATED GLASS

Vibration tests on small samples have been used to obtain the critical frequencies and loss factors of 7 mm, 9 mm and 11 mm laminated glass. The Sound Reduction Index (SRI) as a function of frequency has then b een predicted using Sharp's method The predictions have been compared with measured values of SRI obtained from reverberant room tests on 1. 25 by 1.5 m windows. The predictions are good, particularly of the cri tical frequency and of R(w). The measured SRI exceeds the mass law, po ssibly as a result of the relatively small window size in relation to the depth of the test aperture. The prediction method needs refining i n the vicinity of the critical frequency.