On the Performance of Active Noise Control FX-LMS and FBFX-LMS Algorithms for Duct Network Noise Attenuation

This paper develops an active noise control system (ANC) prototype to be used over a duct network model. The FX-LMS and FBFX-LMS algorithms were implemented using the TMS320C50 fixed point DSP system. Test results show that the FX-LMS algorithm achieves attenuations of up to 43 dB (at 300 Hz) and a mean attenuation of 38.72 dB for frequencies from 100 to 450 Hz. On the other hand, the FBFX-LMS algorithm achieves a mean attenuation of 31.52 dB for the frequency range from 100 to 450 Hz. Moreover, the step size parameter mu was optimized experimentally to obtain the maximum possible attenuation in the frequency range from 100 to 500 Hz. The best possible value for mu was 2048 and the optimized number of filter coefficients was M=128. Finally, the performance analysis illustrates the simplicity of the fixed point DSP solution in the ANC duct network noise cancellation systems.