Flanking paths of a floor–ceiling assembly in wood frame constructions: Measurements and predictions using statistical energy analysis

Abstract

This paper examines the net sound isolation of a floor–ceiling assembly and the supporting walls that might be found in wood frame apartment constructions. The specimen was constructed in the flanking transmission facilities of the National Research Council of Canada. Measured results show that the presence of two load-bearing walls introduce flanking paths that can reduce the net sound isolation of an FSTC 59 floor–ceiling assembly by 6 FSTC points. Various methods of modeling the structural transmission at the floor–wall intersection are presented. The models indicate that beams at the joint (i.e., joist header, head, and sole plates) introduce significant high-frequency joint attenuation due to rotational and shear inertia. Comparison between measured and predicted velocity level differences indicates that floor–wall intersection in standard wood frame constructions should be modeled as two corner joints [(1) upper party wall to floor decking, (2) floor decking to lower party wall] sharing a common plate (the floor decking). A statistical energy analysis model is used to show that the dominant flanking path is the floor decking to the load bearing wall below, while the wall–wall flanking path is much less important. The predictions are shown to be in good agreement with measured results. a)Present address: Shuller International, 10100 West Ute Ave., Littleton, CO 80127.