Floating Floor Attenuation of Impact Structure-borne Sound in Timber Construction

Abstract

The transmission of footfall-excited impact sound is commonly reduced using floating floors. The most basic of these constructions contains three layers – a resilient material, a load-bearing floor, and a floating slab. According to a literature review, a single degree-of-freedom (SDOF) vibration isolation model theoretically predicts impact sound reduction when assuming harmonic loading and a rigid load-bearing floor. However, for timber layers excited by transient loading (e.g. footsteps), sound reduction estimations may contain uncertainties due to inadequate modeling of footsteps and/or floor components. Therefore, this research presents a technique for modeling timber floating floors, as multiple degree-of-freedom (MDOF) systems, using the rigid body dynamics software Working Model 2D® (WM2D). WM2D is first used to verify the SDOF case, by comparing software-generated impact sound reduction plots to graphs found in the literature. Results show agreement between both sources, though with slight error in predicting resonance values. Next, an MDOF model is created with a transversely orthotropic and flexible timber load-bearing floor along with mechanical systems representing the footstep and resilient layer. The impact sound reduction graph for the MDOF system achieves higher values than the SDOF case, which can be attributed to additional resiliencies from flexible beams. Also, regions within the graph resemble the sound reduction plot for the SDOF case.