The influence of catalytic converter on calculated insertion loss of a muffler was investigated. Results show that with the increase of the quantily of catalytic converter

the calculated insertion loss is very close

which is not related to the acoustic source impedance model. To obtain more accurate results of insertion loss

it is necessary to extract the acoustic source impedance

but the difference is negligible in engineering application. On the basis of this feature

a time domain non-linear simulation method of insertion loss is setup. The method not only simplifies the calculation model of insertion loss

but also considers the influence of temperature and air flow on insertion loss

and has high precision

which can optimize the layout of the exhaust system in the concept stage.