Micro-perforated mufflers based on the Acoustic Black Hole effect

Abstract

Attenuation of acoustic disturbance with compact and low-weight acoustical devices is a demanding requisite in industries such as vehicle exhaust mufflers, turbofan liners or ventilation systems. Acoustic Black Holes (ABH) is a concept that has been studied originally in the field of vibration control for the design of a structure based on a power-law thickness profiles along its edges. The idea of wave trapping and dissipation has been extended to the field of duct acoustics using compact devices that avoid blocking the air flow. Based on this idea, in this work we propose the study of a micro-perforated silencer that should prevent reflection and transmission of the sound waves over a wide range of audible frequencies. The use of micro-perforations over the facing cavities should help to extend performance towards the low frequency range. The acoustic behavior of the ABH is assessed from theoretical and numerical modeling. The performance can be greatly improved when the physical constituting parameters are optimized simultaneously. Particle swarm optimization is a computational method inspired by the behavior of natural systems that is able to provide a satisfactory solution with enhanced total dissipation.