Sound Rating Information


Do you have sound rating information for floor truss assemblies (i.e., STC and IIC ratings)? We are looking specifically for ratings for 12 in. floor trusses, with 1 and 1/2 in. concrete topping and without the topping. We are looking to meet the minimum code rating of STC 45 and IIC 45.


Gypsum Association’s Fire Design Manual (GA-600) includes sound ratings for many of the assemblies it lists. In general, sound transmission and impact insulation characteristics of a floor assembly can be calculated by adding up the value of the individual components.

The Sound Transmission Class (STC) method of rating airborne sounds evaluates the comfortability of a particular living space. The higher the STC, the better the airborne noise control performance of the structure. An STC of 50 or above is generally considered a good airborne noise control rating.

Impact sound transmission is produced when a structural element is set into vibration by direct impact such as by someone walking. The vibrating surface generates sound waves on both sides of the element. The Impact Insulation Class (IIC) is a method of rating the impact sound transmission performance of an assembly. The higher the IIC, the better the impact noise control of the element. An IIC of 55 is generally considered a good impact noise control rating.

The contributions of various products to an STC and IIC rating are shown in SBCA’s Metal Plate Connected Wood Truss Handbook.

For additional information on design techniques to reduce noise levels, see Owens-Corning’s Noise Control Guide.

SBCA Categories: