BAND-GAP CHARACTERISTICS OF ONE-DIMENSIONAL DUCT PERIODICALLY MOUNTED HELMHOLTZ RESONATORS WITH BUILT-IN BAFFLE AND INTUBATION

摘要

Traditional Helmholtz resonator is often applied to reduce noise in a narrow frequency band. In order to expand noise attention band, combing the band gaps in phononic crystal pipe which can forbid wave propagation is an effective way. In this paper, the sound transmission loss (TL) and band structure of the Helmholtz resonators with built-in baffle and intubation mounted periodically are investigated theoretically and numerically. The transfer matrix method (TMM) of one-dimensional and two-dimensional and the finite element method (FEM) are proposed to conduct the investigation. It is shown that the two-dimensional TMM is more accurate within the study frequency range. Then the TL and band structure predicted by this method are presented. It illustrates that the introduction of baffle and intubation could generate two resonant peaks in TL compared with the traditional Helmholtz resonator. And the wave scattering and resonance induce the Bragg and locally-resonant band gaps in the periodic pipe, respectively. Further analysis on the effect of variable parameters including the lattice constant, the length of the intubation, and the location of the baffle are conducted. The research provides a new way to the low-frequency noise control.