A TIME DOMAIN SOLUTION FOR THE ATTENUATION, AT HIGH AMPLITUDES, OF PERFORATED TUBE SILENCERS AND COMPARISON WITH EXPERIMENT

A numerical method, for determining the sound transmission loss of perforated tube silencers in the exhaust systems of internal combustion engines, is described; mean fluid flow and intense sound are allowed for in the analysis. The quasi-one-dimensional equations governing the sound field are approximated in finite difference form and are solved in the time domain. This is because non-linear hydrodynamic effects at the orifices need to be taken into account, and a time domain solution is a versatile way of doing this. Transmission loss data measured on two experimental silencers are presented alongside numerical predictions and agreement is shown to be good. Comparison is made between the present scheme and an equivalent frequency domain analysis and it is seen that the time domain method gives superior predictions of the transmission loss.