LOW FREQUENCY SOUND PROPAGATION IN A COAXIAL CYLINDRICAL DUCT: APPLICATION TO SUDDEN AREA EXPANSIONS AND TO DISSIPATIVE SILENCERS

A method based on the approximation of the radial pressure profile is developed to analyze the acoustic performance of a sudden expansion and of an expansion chamber at low frequencies. This model is able to predict very accurately the added length of an expansion which includes neither porous material nor a perforated tube. It can also be applied when a bulk-reacting lining and perforated tube are included. This model of a dissipative silencer gives results which compare very favourably with experimental data.