The results of current studies of intake and exhaust noise from piston engines are described in the context of intake and exhaust system acoustic design. The objectives combine the achievement of sound emission targets with the maintenance of optimum engine performance and fuel efficiency throughout a specified range of operating conditions. Practical experience demonstrates that the relevant technology includes a quantitative evaluation of those factors directly concerned with engine operation and breathing, those factors influencing the excitation and propagation of pressure waves through the relevant system and those factors controlling the emission of sound to the surrounding environment. A summary is provided of previous and current developments in appropriate existing numerical codes for performing the detailed calculations and associated performance assessments with increasing realism. (C) 1999 Academic Press.