Acoustic characteristics of engine air cleaner boxes

Air cleaner boxes placed on the induction system of engines play a critical role in the attenuation of airborn sound. The acoustic performance of such configurations is investigated experimentally and computationally in the absence of mean flow. The transmission loss of a fabricated rectangular box (prototype) with various inlet and outlet locations and extensions is predicted by a three‐dimensional boundary element method. The predictions are then compared with experimental data obtained from an impedance tube setup. The results demonstrate that: (1) the variations of locations and extension lengths of inlet and outlet affect the acoustic behavior of the prototype at higher frequencies, as expected; (2) the transmission loss characteristics at low frequencies may be estimated by a one‐dimensional analysis; and (3) the boundary element method is effective throughout the entire frequency range of interest in predicting the acoustic performance of air cleaner boxes with asymmetric shape and/or inlet and outlet extensions.