Performance of a modified double expansion chamber muffler inspired by Acoustic Black Hole theory

Mufflers are used for reducing the noise emitted by the exhaust system of an internal combustion engine. A double expansion chamber is one method to improve the noise reduction performance of a muffler, but it has low sound reduction performance at specific frequencies due to resonance and requires more space. Recently, it has been proposed that Acoustic Black Hole (ABH) termination in ducts characterized by its power-law profile has a high reflection coefficient at lower frequencies. This study presents numerical and experimental studies of double expansion chamber mufflers with a modified geometry inspired by Acoustic Black Hole theory to improve the low transmission loss and insertion loss performance while simultaneously decreasing the volume of the chamber. Promising initial results suggest the potential for application of ABH in muffler design.