This paper gives the results of 27 laboratory measurements of the sound insulation of 75mm thick tongue and groove autoclaved aerated concrete (AAC) panels with stated nominal dry density of 510kg/m3 (a surface density of 38.2kg/m2).which are lined with 13mm thick gypsum plasterboard. Two configurations that are presently common forms of construction in a region of Australia were tested; 1. Furring channel one side and stud wall the other that maintained an overall wall width of 243mm, and 2. Direct fix one side and stud wall the other. In both cases the gypsum plasterboard is mounted on 64mm steel studs. The gap between the panels and the steel studs is 20, 35 or 48mm. With the exception of one empty cavity, the cavity on this side contains 11kg/m3 glass fibre batts with thickness of 50, 75, 90 or 110mm. On the other side of the panels, the gypsum plasterboard is mounted on furring channels and adjustable clips which are screwed to the panels or in 6 cases directly screwed to the panels. Except for the directly screwed cases, the gap between the panels and the gypsum plasterboard is 30, 43 or 58mm. The cavity is empty or contains 50 or 70mm thick 11kg/m3 glass fibre batts or 25mm thick 24kg/m3 glass fibre batts. The 13mm gypsum plasterboard has nominal surface densities of 7.2, 8.5 or 10.5kg/m2. The aim was to develop a system which has a laboratory measured Rw+Ctr equal to or greater than 50dB which is required by the National Construction Code (NCC) of Australia for walls between separate dwellings. A system with cavities on both sides of the wall is desirable because it allows services to be accommodated without the need for chasing which is not permitted. The undesirable effect is a resultant large Ctr making it difficult to achieve an Rw +Ctr equal to or greater than 50dB.
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