The algorithms on these pages estimate values of sound transmission class (STC) for stud walls of various configurations. One page estimates STC and impact insulation class (IIC) values for joist floors.
The values are estimates of what would be measured in the test facilities at the Institute for Research in Construction, (IRC) of the National Research Council (NRC), Canada. The user should bear in mind that similar sound insulation ratings are only achieved in buildings when careful consideration is given to the design of the junctions between walls and floors so flanking transmission is controlled.
Choose the type of construction you are interested in using the links in the frame on the left. There is a link on each calculation page to a description of the regression analyis results for the particular kind of construction.
Estimates are given as a number with an associated uncertainty that is due to variations in the data and materials. For example, ±2 means that 66% of the measured values for the constructions lay within plus or minus 2 of the estimate.
Most of the calculations are made using regression equations developed from analysis of the results from several large sets of measurements made at the Institute for Research in Construction, (IRC) of the National Research Council (NRC), Canada.
The data from which the regression equations for gypsum board walls were derived are given in internal reports IR-693 and IR-832.
The data from which the regression equations for joist floors were derived are given in internal reports IR-766 and RR-169. These Research reports and other information can be found on the Publications page of IRC's web site.