Numerical method for estimating acoustic radiation from machine elements

Abstract

With the aim of being able to predict the noise radiation from machine elements, numerical methods for estimation of acoustic radiation from vibrating structures in arbitrary modes were investigated, and results for fundamental structures were examined. Numerical Helmholtz integral formulation was applied and formulae for calculating radiation efficiency and radiation loss factor were derived to represent the frequency characteristics of radiation. A practical method for estimating field pressure patterns was also developed that uses plane wave approximation at high frequencies. The lower limit of this plane wave approximation is given by the break frequency of the estimated radiation efficiency curve. Numerical solutions for spherical sources in breathing and oscillating modes agree well with the analytical solutions. In addition, radiation factores for cylindrical bars undergoing flexural vibratin were calculated and compared with analytical solutions for infinite bar.