Single-channel Active Noise Control Systems Research Articles

Mitigating wind noise in multichannel active noise control systems

Multichannel active noise control (ANC) systems have been investigated to reduce outdoor low-frequency noise, such as power transformer noise and traffic noise. However, in outdoor environments, wind noise is inevitable and significantly degrades the noise reduction performance of active control systems. Despite broad adoption in windy environments, porous microphone windscreens cannot eliminate low-frequency wind noise in microphones, especially when the wind speed is high. Assuming wind noise is additive and uncorrelated with the primary noise to be controlled, this paper analyses how the wind noise detected by the reference microphone impacts the control filters and the residual noise of a multichannel ANC system based on the multichannel filtered-reference least mean squares algorithm (MFxLMS). By extending our recent research on wind noise suppression in single-channel active noise control systems [Y. Chu, et al., J. Acoust. Soc. Am. 152(6), 3340–3345 (2022)], a modified MFxLMS algorithm based on a new cost function is proposed. Simulations with real-recorded wind noise are performed to verify the theoretical analysis.

Effect of a tilting reflective plane on the performance of an active noise control system

This article presents the results of an investigation of the noise reduction performance of a single-channel active noise control system in the presence of a tilting reflective plane. It is shown that the noise reduction achieved by the system depends upon the orientation angle of the panel and on the separation distances between both the primary and the secondary source and the reflective panel. It is also observed that the maximum noise reduction is obtained when the reflective panel is vertical and when the separation distance is less than about 0.13 of the wavelength at the frequency of interest. When the panel is moved away, the maximum noise reduction occurs at other tilting angles. Experiments were carried out in a real living room which is close to real-life situations. It is found that there is an improvement in the extent of the quiet zone in the presence of the panel. The reduction in sound pressure level is also better with the reflective panel, which is up to 20 dB.

Implementation of a single-channel active noise control system with multiple reference sensors

When multiple sources contribute competitively to the noise level, multi-channel control architecture is needed, leading to more cost and time for control computation. We, hence, are concerned with a single-channel control method with a single-reference signal obtained from a linear combination of the multiple source signals. First, we selected 3 source signal sensors for the reference signals and the error sensor, selected a proper actuator and designed the controllers: 3 cases of single-channel feedforward controllers with a single-reference signal respectively from the source signals, a multi-channel feedforward controller with the reference signals from the source signals, and the proposed controller with the reference signal from weighted sum of the source signals. The weighting factors and the filter coefficients of the controller were determined by the FxLMS algorithm. An experiment was then performed to confirm the effectiveness of the proposed method comparing the control performance with other methods for a tower air conditioner. The overall sound pressure level (SPL) detected by the error sensor is compared to evaluate their performance. The reduction in the overall SPL was obtained by 4.74 dB, 1.96 dB and 6.62 dB, respectively, when using each of the 3 reference signals. Also, the overall SPL was reduced by 7.12 dB when using the multi-reference controller and by 7.66 dB when using the proposed controller. Conclusively, under the multiple source contribution, a single-channel feed forward controller with the reference signal from a weighted sum of the source signals works well with lower cost than multi-channel feedforward controller.

A robust approach for online feedback path modeling in single-channel narrow-band active noise control systems using two distinct variable step size methods

Online feedback path modeling and neutralization (FBPMN) is vital in active noise control (ANC) systems to ensure stability and elevate performance in non-stationary environments. In this paper, we propose a modified variable step size (VSS) method for online FBPMN in single-channel ANC systems which incorporates three adaptive filters; a noise control filter, a FBPMN filter, and a linear predictor for disturbance removal. In the proposed method, distinct VSS LMS algorithms are used for FBPMN filter and disturbance removal filter to achieve exceptionally fast convergence and accurate modeling of the feedback path transfer function. Simulation results show that the proposed method yields a significantly more robust ANC system by attaining a higher gain margin at a much faster rate in comparison with the existing methods.

755 ルーバとスリットを持つ開口部における能動騒音制御に関する研究(低騒音化技術I,OS-4 音響・振動,総合テーマ「伝統を,未来へ!」)

The purpose of this study is about noise reduction by Active Noise Control (ANC) at the opening with a louver which attached Piezoelectric Card Speaker. In a house and an apartment not only machinery, louvers are used at large opening aimed for air conditioning and ventilation. Leakage of a sound from the opening set louver becomes a problem. In this experimental study, proposed ANC system is independent parallel control system using two single channel ANC systems. One of them, secondary noise source is set at each bane down side of louver. The other one is set slit of enclosure opening. The experimental results show that noise reduction is obtained from 5dB to 25dB in sound field on this proposed ANC system.

A simplified method for online acoustic feedback path modeling and neutralization in multichannel active noise control systems

The presence of strong acoustic feedback degrades the performance of active noise control (ANC) systems, and in the worst case the ANC system may become unstable. In this paper, we investigate additive-random-noise-based methods for online feedback path modeling and neutralization (FBPMN) in multichannel ANC systems. In existing methods, separate filters are used for each acoustic feedback path: one for online feedback path modeling (FBPM), and another for feedback path neutralization (FBPN). Furthermore, the existing method works well for predictable noise sources but its performance degrades for unpredictable sources. This paper attempts to solve these problems in multichannel ANC systems. The proposed method is a modification and extension of previous work for online FBPMN in single-channel ANC systems. In the proposed method, we combine the two tasks of FBPM and FBPN in one online FBPMN filter, and hence, the computational complexity of the proposed method is lower than existing methods. Computer simulations are carried out to demonstrate the effectiveness of the proposed method. It is shown that the proposed method achieves better performance than existing methods for both predictable and unpredictable noise sources. Furthermore, this improved performance is achieved at somewhat reduced computational complexity.

An extension of simultaneous equation method to multiple channel active noise control system

AbstractWhen a region with a certain area needs silencing, no sufficient effect can be obtained with a single‐channel active noise control system. Therefore, multiple channel noise control systems using several microphones and speakers have been proposed. One of the algorithms used frequently is the Multiple Error Filtered‐X (MEFX) method. The MEFX method requires prior estimation of the error path system. In the case of multiple channels, the estimation error poses more complex effects in comparison to the single channel. In addition, variations of the system during operation are problematic. In this paper, the simultaneous equation method recently proposed for the single channel in which no estimation is required for the error path system is applied to the multiple channel active noise control. In the present procedure, the coefficients of the noise control filter can be estimated without estimation of the error path system as in the case of the single channel. The method can handle the variation of the path during operation and can obtain excellent silencing effects. © 2002 Scripta Technica, Electron Comm Jpn Pt 3, 85(5): 46–55, 2002