Acoustic attenuation characteristics of the muffler phononic crystal with hybrid resonators

Aiming at achieving broadband and strong sound attenuation in the duct, this study proposes one compact and hybrid muffler phononic crystal. The two-dimensional (2D) transfer matrix method is applied to calculate the transmission loss (TL) of one unit cell validated by the numerical simulation and experiment. On this basis, the unit cell dispersion theory is employed to predict the bandgap properties of the infinite periodic mufflers. The sound reduction mechanism in the hybrid muffler is disclosed, while the effect of the period number on the acoustic performance is examined. It demonstrated that the acoustic resonant behaviors of the short-length mufflers are conducive to the continuous and superior attenuation band through the compact structure. The number of the TL domes and the boundary length of the short chamber could be evaluated by the cut-off fre-quency at the (0,1) radial mode and the first passing frequency for the muffler. Although each resonant-type component of the hybrid muffler is responsible for the TL peaks at different frequency ranges, via the coupling effect, they provide remarkably improved performance over a wide frequency range. The unit cell periodicity brings two types of bandgap, the locally resonant bandgap (LRG) and Bragg bandgap (BG), further enhancing the attenuation amplitude. Utilizing the different resonance mechanisms as well as the merging of the LRG and BG, the hybrid muffler phononic crystal is improved, which possesses a wide attenuation range with a tinier structure. The results develop new approaches for broadband and strong sound attenuation using the concept of the phononic crystal and offer a promising application in duct noise control.

Automated summary

This study proposes a compact and hybrid muffler phononic crystal to achieve broadband and strong sound attenuation. The transmission loss (TL) of a unit cell is calculated using the 2D transfer matrix method and validated through numerical simulation and experiment. The study reveals the sound reduction mechanism and examines the effect of the period number on the acoustic performance. The results show that the compact structure of the short-length mufflers enables continuous and superior attenuation band through acoustic resonant behaviors.