Sound insulation of double walls - An experimental parametric study

The sound insulation of double panels has been widely studied in the literature so far. In most previous studies, only one or two double wall parameters are dealt with at a time and the overall comprehension of the behaviour of the double panel can be lost. For example, studs are often ignored. The purpose of this study is to strengthen our all-inclusive understanding of double panels. The study was implemented by means of a carefully planned experimental parametric study. Altogether 54 sound insulation tests were done with double panels where the cavity properties were changed. The panel material was 2-mm thick steel to obtain a high critical frequency. The most important parameters for uncoupled structures were the amount of absorbent and the cavity thickness. The flow resistivity of the mineral wool did not play a significant role. For coupled structures, the stiffness (or type) of the stud, and the spacing of the screws between the panel and the stud were the most important parameters. Flexible studs were better than rigid studs at low and middle frequencies but the difference was smaller at high frequencies than expected. The stud spacing did not play a significant role except at low frequencies, when dense stud spacing was used. In this case, very strong low frequency resonance occurred. The resonance is probably caused by horizontal normal modes of the sub-panels, which are formed between vertical studs. This resonance and the effects of stud stiffness and screw spacing should be further investigated in the future.