External pressure loading, vibration, and acoustic responses at low frequencies of building components exposed to impulsive sound

Abstract

This paper presents the formulation and experimental validation of a numerical tool that can predict: (1) the external pressure loading due to impulsive sound generated by an outdoor point source and (2) the resulting fully coupled vibro-acoustic response at low frequencies of a two-dimensional building component (e.g. wood-framed wall with windows) backed by a rigid rectangular cavity. The model allows for the building component to have arbitrary geometry and boundary conditions. Assuming linear-acoustic propagation and acoustically rigid surfaces, the external pressure loading is computed with a three-dimensional numerical model, in the time domain, by combining the image-source method for the reflected field (specular reflections) with an extension of the Biot–Tolstoy–Medwin (BTM) method for the diffracted field. The fully coupled vibro-acoustic response of the fluid–structure system is computed in the time-domain using a modal-decomposition approach. The natural frequencies and mode shapes of the structure are computed with a finite-element model based on shell theory. Acoustic natural frequencies and mode shapes of the cavity are computed analytically assuming hard-wall boundary conditions. The experimental validation of the numerical model is also presented. Experiments were conducted on wood-framed walls without and with a window using a speaker to generate N-waves and load the walls structurally. It is found that numerical simulations are in good agreement with experimental data for these two cases.