An active noise control method for ducts is proposed to overcome the acoustic feedback problem occurring between detect sensor and control speaker in conventional control systems. In this study, time domain acoustic signals detected from two adjacent microphones are decomposed into positive and negative-going waves in frequency domain, and they are utilized in updating two FIR filters for the main system and feedback one. Consequently, wave decomposition in frequency domain enables the picking only the downstream wave up very easily with simple arrangement. Experimental result shows that frequency domain adaptive filter (FDAF) algorithm using wave decomposition has the same amount of noise reduction as that of filtered-x algorithm. In addition, it is found that the proposed control strategy is very robust to external disturbance and one can possibly to select different adaptation constants for interested range of frequencies. Therefore, the present method can be used as an effective active noise control method instead of previous algorithms and control system layouts without any degradation of the acoustic performance.
