Analysis of an Ultra-Low Frequency and Ultra-Broadband Phononic Crystals Silencer with Small Size

Abstract

Existing research shows that acoustic BG in a certain frequency range can be realized by installing an expansion chamber on duct system, but the problems of broadband and size limitations at low frequencies remain to be researched. The study of acoustic and elastic wave propagation in artificial periodic structures has received increasing attention for many decades, and the presence of bandgap (BG) in phononic crystals (PCs), which inhibits elastic/acoustic wave propagation within the BG’ frequency range, supplies a new way to control noise and vibrations in duct system. Based on PC theory, a duct silencer backed with a gas–liquid expansion chamber is proposed to enhance the acoustic performance of low-frequency noise attenuation. The transfer matrix method (TMM) is used to investigate the acoustic BG properties. The influences on the BG properties of some key parameters are analyzed, and the band formation mechanism is revealed by the law of energy conservation. The results show that silencers with a small size can effectively attenuate ultra-low frequencies and ultra-broad bands.