Simulation of Vehicle Pass-by Noise Radiation

Abstract

This paper presents an extended Kirchhoff integral formulation for predicting sound radiation from an arbitrarily shaped vibrating structure moving along an infinite baffle. In deriving this formulation, the effect of sound reflection from the baffle is taken into account by using the image source theory. Moreover, the effect of source convection motion and that of motion-induced fluid-structure interaction at the interface on the resulting acoustic pressure field are considered. The formulation thus derived is used to calculate sound radiation from a simplified vehicle model cruising along a solid ground at constant speeds. Since analytical and benchmark numerical solutions for an arbitrarily shaped vibrating object in motion are not available, validations of numerical results are made with respect to those of a point source. Next, sound radiation from a full-size vehicle is simulated. For simplicity, the vehicle is assumed to be made of a shell-type structure and excited by harmonic forces acting on its four tires. Vibration responses subject to these excitations are calculated using finite element method (FEM) with HyperMesh® version 2.0 as pre- and post-processors. Once the normal component of the surface velocity is specified, the radiated acoustic pressure fields are determined using boundary element method (BEM). Numerical results show that the effect of source convection motion enhances sound radiation in the forward direction, but reduces that in the rearward direction. Changes in the resulting sound pressure fields become obvious when the Mach number exceeds 0.1, or equivalently, when a vehicle cruises at 70 mph or higher.