HYBRID BROADBAND SILENCER

A silencer in compact configuration controlling broadband noise including low frequency regime remains a technical challenging. In this study, a silencer which is composed of passive and active system is proposed. For the passive system, micro-perforation is introduced into the plate silencer. Drilled with sub-millimetre holes, the micro-perforated plate aims to elicit the sound absorption in order to compensate for the deficiency in the passband caused by the insufficient sound reflection in a certain frequency range due to weaker plate stiffness. Through proper balancing between sound absorption and reflection, the plate silencer with micro-perforation provides a more flattened and uniform TL and a widened stopband by more than 20%. For the active system, piezoelectric actuator is introduced to the system of the plate silencer with micro-perforations, leading to a so-called hybrid passive and active noise control system. The aim for adding the active part is to further broaden the effective range of the plate silencer with micro-perforation to even lower frequencies. To realize the goal, an additional plate attached with piezoelectric actuators is inserted to the plate adjacent to the original micro-perforated plate and backed by an independent rigid cavity. The hybrid system is investigated under passive and active operation modes. It is shown that the lower limit of the working range of the plate silencer with micro-perforation can be further extended to the low frequency with a reasonable control voltage under relatively simple control strategy.