Sound transmission loss of gypsum wallboard wall partitions

Using the data bank of the acoustic laboratory of Domtar Research, statistical equations based on frequency and surface density were derived for predicting sound transmission loss (STL) and sound transmission class (STC) of double leaf wall partitions constructed using gypsum wallboard and either steel or wood studs. The equations show close agreement with experimental data for all frequency bands except those near the coincidence dip. Results predicted using these equations also agree closely with experimental results published by other laboratories. Using these equations the effect of frequency, surface density and cavity filler on STL and STC is easily seen. However, the study also revealed some unexpected results whether or not a partition was (1): Balanced- as to board placement did not significantly affect the STC of either steel or wood stud partitions. (2) For multilayer wood stud partitions attaching the second layer of board to the first with screws, rather than using glue, dramatically reduced the STL at higher frequencies. For higher surface density partitions this decrease may negate any benefits to be derived from adding fiberglass to the cavity space.