This report covers work carried out during the second phase of an investigation into Flow Generated Noise and Pressure Losses in heavy vehicle silencer systems which forms part of the QHV90 Project. In the first phase, many silencer components were tested and a scheme for predicting Flow Generated Noise (FGN) and Pressure Drop (PD) in simple silencer elements was established. During the second phase, work has been carried out to improve the quality and supplement data needed to make accurate predictions of FGN and PD; modifications to reduce these have also been assessed. Practical use of the methods for making predictions were studied by testing Manufacturers Silencers and guidelines have been developed. Much of the phase I data is now superseded and so a design guide has been produced for the silencer manufacturer. The guide combines the findings of phases I and II and is written so that it can be used separately from this report. (A)

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