Sound Pressure Levels Generated by Internal Combustion Engine Exhaust Systems

A computer program has been developed which predicts the sound pressure level and the frequency spectrum produced by simple engine exhaust systems. The program utilizes unsteady flow gas dynamic theory to predict the pressure-time history in the exhaust system and the velocity-time history at the open end of the system. Acoustic theory is then used to predict the sound pressure levels and frequency spectrum in free space.

The work was carried out on a twin-cylinder four-cycle engine, but the theory can be applied to any internal combustion engine.