Flow noise from exhaust systems is a noise source that contributes to drive-by noise measurements. A prediction tool that allows us to choose the right duct dimensions would be very helpful. Therefore we integrated a flow noise module in a given linear acoustic prediction software.A flow noise source is modelized as an acoustic source. The source spectra is a function of the Strouhal number. The noise level depends on flow speed. A flow noise measurement with cold flow gives a set of source describing parameters. Using these parameters and the flow noise source model, a prediction of flow noise for mufflers is possible.