Numerical modelling of wood frame joints having fire stops

Abstract

In a companion paper (1994) the degradation of the net air borne sound isolation resulting from the flanking path caused by a special class of fire stops was investigated. This paper examines a simple model for the propagation of bending waves through the joint involving a fire stop constructed by continuing one of the room's surfaces across or under the nominally separating element. It shows a simplified section through the partition wall and the end wall that will be modelled. Due to the symmetry of the joint it can be viewed as a pair of corner joints coupled by an element (i.e., the fire stop) having a unique bending stiffness. In the simplified model presented, only the transverse component of the surface velocity is considered as it is this motion (i.e., that caused by bending waves) that will be, by far, the most effective at converting structural vibration to airborne acoustic energy