Hybrid noise control using multiple Helmholtz resonator arrays

Helmholtz resonator (HR) is one of the most basic acoustic models and is generally used to reduce low-frequency noise. However, it is only effective at its single resonance peak with narrow frequency band. In order to deal with low-frequency, broadband and hybrid noise in a ventilation ductwork system, a multiple HR arrays system is therefore proposed in this paper. Several tuned HRs mounted on the same cross-sectional area of the duct is considered as a transverse HR array. By distributing the transverse HR array periodically along the duct, the multiple HR arrays system is then proposed to eliminate hybrid noise in a ventilation ductwork system. The acoustic performance of the proposed multiple HR arrays system is analyzed theoretically and numerically. The transfer matrix method and the Bragg theory are used to investigate wave propagation through the duct. Owing to the coupling effects of the Bragg refection and HRs’ resonances, several broadband noise attenuation bands can be obtained. The theoretical predictions show good agreement with the three-dimensional Finite Element Method (FEM) simulation results. The present study provides a practical way in hybrid noise control application of the ventilation ductwork system and other research areas in respect of the HR.