Environmental noise control by Parallel Barriers integrated withHelmholtz Resonator

Tins paper deals with the noise reduction degradation problem of parallel barriers with the rigid walls used in the traffic noise control. Various studies have shown that the insertion loss at the receivers is significantly deteriorated due to multiple reflections between the parallel reflecting surfaces. The degradation is attributed to the resonances within the semi-enclosed domain bounded by the parallel barriers and the rigid ground. To understand the physics behind, the modal equation of the parallel barriers system is obtained. The eigenfunctions governing the sound field can be expressed as the finite sum of the coupled enclosure modes and the radiation modes. In order to improve the performance of parallel barrier especially at the deteriorated frequencies, the optimal designed Helmholtz resonator is adopted to modify the acoustic mode. Numerical results in two dimension indicate that single resonator can suppress more than one resonant peak and hence improve the insertion loss. In addition, two resonators at different frequencies can significantly enhance the noise reduction in the frequencies ranging from 200 Hz to 1000 Hz.