Reactive muffler with additional U-shaped cavities

Abstract

This work emphasized on the enhancement of acoustic performance of a flow through reactive muffler. The sound transmission loss and insertion loss were improved by an inclusion of specific design cavities within the muffler. Some acoustic filters were combined in the available limited space of muffler in the form of U-shaped cavity. This inclusion structure consisted of Helmholtz resonators, perforated plates, and U-shaped resonator. There were two perforated muffling sections which were placed on the main duct and on the plate within the designed cavity. Variation of the perforation ratio on the perforated plate was also analyzed. During experiment, four-microphones method was implemented to measure the muffler model performances. It found that the proposed U-shaped cavities can increase acoustic performance of reactive muffler with the average sound trasmission loss is up to 58 dB. It also brings opportunity for customising every muffling section to works on certain frequency band with a spoecific resonance characteristics in regards to the inner structure of cavities of muffling sections.