The experimental investigation of the sound transmission loss (STL) through the thin aluminium panels with lumped masses, ribs and absorptive layers was made. The STL through the double paralleled membranes was also experimentally studied. In the experiments, it was observed that
(1) the effects of mass-attachment to the panel were not significant,
(2) rib-attachment to the panel increased STL below about 2.6k Hz,
(3) the absorptive facings were more effective in STL when attached on the receiver-room side of the panel than on the source-room; and
(4) to find the effects of the gap distance of the double paralleled membranes, two 0.1mm thick vinyl membranes were used. As the gap increased, the increase in STL beyond higher than 1.25k Hz was observed.
