Active Suppression of Narrowband Noise by Multiple Secondary Sources

Abstract

This study presents theoretical and experimental investigation on the active suppression of narrowband noise with C1, C1.5, and C2 components by using multichannel secondary sources in a duct. The quality manipulation in the duct was controlled by changing quality factors which were incorporated into a multichannel FxLMS algorithm. The algorithm is extensively investigated in both theory and real-time control experiment. After analysing the primary and secondary paths of the duct system, an acoustic narrowband signal was chosen as a primary noise and the impulse responses were implemented as the secondary path models. Control results show that the quality factors in the algorithm that was implemented in a dSPACE 1104 provide a stable and excellent response compared to before control. It is obvious that the lower quality factor cancels the more primary noise as defined in the theory although the attenuation levels are not exactly and inversely proportional to the quality factor. The results in this study can be used for practical active sound quality control systems.

Review of active noise control techniques with emphasis on sound quality enhancement

“…A proper introduction of the second adaptive filter is extremely important to weaken the passband disturbance [91][92][93]. Based on the FxLMS [94], an upgraded algorithm called the filtered-error least-mean-square (FELMS) was proposed in the literature [95,96], which can effectively compensate for the deficiency of the FxLMS algorithm. Fig.…”

Length Variation Effect of the Impulse Response Model of a Secondary Path in Embedded Control

“…where is the IRF filter length of̂( ) andŝ is the coefficient of the IRF filter. The update equation of an adaptive feedforward narrowband FxLMS algorithm can be written by [1][2][3][4] w ( + 1) = w ( ) +x ( ) ( ) ,…”

“…An ANC system requires a good model for the compensation of the secondary path (or the plant) when the filtered-x least mean square (FxLMS) algorithm is used. It is known that the accuracy of the secondary path model has a decisive influence along with the convergence coefficient on the performance, stability, and convergence speed of the ANC system [1,4]. The impulse response function (IRF) of the secondary path of the FxLMS approach is usually implemented as an FIR (finite impulse response) filter in a real-time embedded control board because the FIR filter is stable and easy to implement.…”