Analysis and DSP implementation of a broadband duct ANC system using spatially feedforward structure

The active control technique for broadband attenuation of noise in ducts, u sing spatially feedfoward structure. is investigated from the viewpoints of both acoustic analysis and exists an ideal controller for this problem. Th e ideal controller is a function of the finite control engineering. Accordi ng to the previous work by Munjal and Eriksson [1], there source impedance and is thus independent of the boundary conditions. Despite the simplicity the ideal controller cannot be practically implemented due to the difficult y of calibration of electro-mechanical parameters. To overcome the problem, the controller is implemented via an equivalent formulation modified from the controller originally proposed by Roure [2]. The modified controller is implemented on a DSP platform, using a FIR filter, an IIR filter and a hyb rid filter. The experimental results showed that the system achieved 17.2 d B maximal attenuation in the frequency band 300 similar to 600 Hz. Physical insights and design considerations in implementation phase are also discus sed in the paper.