Hybrid Active Noise Control System Research Articles

A novel feedforward narrow-broadband hybrid active noise control system for excavator interior noise control

Excavator interior noise is a mixture of engine noise and impulsive noise produced by working device. Hybrid narrow-broadband active noise control (HANC) systems can efficiently eliminate the traditional mixed broad-narrowband noise. However, these HANC systems have drawbacks such as high computational complexity, unable to cope with impulsive noise and inability to obtain the best performance due to parameter selection method. To solve these problems, a novel feedforward narrow broadband HANC system consisting of four subsystems, namely, sinusoidal noise canceller (SNC) subsystem, robust broadband active noise control (RBANC) subsystem, delay narrowband active noise control (DNANC) subsystem, and supporting error calculating subsystem, is proposed. Combining the advantages of delayed least mean square algorithm in DNANC subsystem and Versoria criterion-based filtered-x least mean square algorithm in RBANC subsystem, both the computational efficiency and the robustness when encountering impulsive noise of the proposed HANC system are efficiently improved. In addition, the performance of the proposed HANC system is further improved by changing the key parameters selection method form trial-and-error method to improved particle swarm optimization (IPSO) algorithm with active factor. Both the superiority of the proposed HANC system over existing counterparts and the advantage of the IPSO algorithm with active factor in determining the key parameters are demonstrated by extensive simulations. Real-time HANC experiments in semi-anechoic chamber based on measured excavator interior mixed noise are conducted in this article. Experimental results illustrate that the proposed HANC system achieves good noise elimination performance and also being robust when encountering impulsive noise.

A semi-adaptive feedforward hybrid active noise control algorithm for multichannel systems.

Broadband active noise control systems incorporating fixed controllers exhibit limited ability to reduce sinusoids. This study presents a semi-adaptive feedforward hybrid active noise control (HANC) system to address this issue. The proposed system pairs fixed high-order optimal controllers for broadband noise with adaptive low-order FXLMS-based controllers for narrowband noise. Notably, parallel broadband and narrowband controllers work independently. The proposed semi-adaptive feedforward HANC system demonstrates low computational complexity which makes it suitable for multichannel systems. Simulations and experiments validate the effectiveness of the proposed system in controlling mixed noise.

Hybrid Active Noise Control with Auxiliary Filter-based Virtual Sensing

In this paper, we propose a hybrid active noise control system with auxiliary filter-based virtual sensing. The proposed system consists of a Feed-Forward (FF) part, which can reduce broadband noise, and a FeedBack (FB) part, which can reduce narrowband disturbance components, by introducing virtual sensing into the hybrid ANC. Virtual sensing is realized by using two auxiliary filters because the optimal noise control filters are different for the FF and FB parts, respectively. These auxiliary filters store information on the optimal noise control filters that can reduce both narrowband disturbance and broadband noise at the desired location in the tuning stage. Through simulations with real impulse responses for real applications, we demonstrate that the proposed hybrid ANC can achieve an overall noise reduction of about 30 dB.

Theoretical convergence analysis of the FXLMS-based feedforward hybrid active noise control system

Real noise typically includes both broadband and narrowband components, such as noise generated by rotating machines. The feedforward hybrid active noise control (FFHANC) system reduces both components separately by arranging broadband and narrowband controllers in parallel. Although considerable efforts have been made to improve the FFHANC system, a theoretical analysis of its performance is still lacking. Consequently, the application of the FFHANC system lacks a solid foundation. Furthermore, the stability bounds of step sizes that guarantee convergence are not available in the literature. To address these problems, a convergence analysis of the FFHANC system based on the filtered-x least-mean-square algorithm is proposed. The analysis of the mean and mean-square convergence behaviors of the weight errors theoretically illustrates the advantages of the FFHANC system in terms of fast convergence and high reduction. The mutual coupling of parallel controllers in the mean-square sense is derived and discussed. By predicting the steady-state mean-square error and stability bounds, the proposed model can also guide the choice of step sizes. Our analysis lays the theoretical foundation for the practical application of the FFHANC system. Extensive simulations are performed to demonstrate the validity of the proposed theoretical theory.

A study on hybrid active noise control system combined with remote microphone technique

This paper proposed a hybrid active noise control (HANC) system combined with virtual sensing technique. The Remote Microphone Technique (RMT) method was established in the time domain, and the optimal array of observation sensors of RMT method was determined by Genetic Algorithm (GA). Then with the pre-defined observation filter, a multichannel simplified HANC system combined RMT (msHANC-RMT) method was proposed. The off-line simulations were executed with the data collected from the tests in a semi-anechoic chamber. The results showed that the msHANC-RMT system had the similar control capability compared to the msHANC system in all noise conditions, which can further compress the peak frequency components in the noise spectrum that cannot be detected and controlled by the traditional feedforward ANC (FFANC) system. However, the msHANC-RMT system was more sensitive to delays compared to the FFANC system, once the additional delays exceeded several milliseconds, the feedback structure in msHANC-RMT system lost most of the control capacity.

A robust feedforward hybrid active noise control system with online secondary‐path modelling

In this study, a robust feedforward hybrid active noise control (ANC) system with online secondary-path modelling (SPM) is proposed that is capable of not only effectively suppressing the broadband and narrowband noise components but also tracking the secondary path (SP) variations. An finite impulse response online SPM subsystem as well as an efficient decoupling filter are included in the proposed feedforward hybrid ANC (HANC) system. The decoupling filter is a parallel-form bandpass filter bank that consists of multiple bandpass filters that are derived from the second-order infinite impulse response notch filters. It takes the residual noise as its input and separates the broadband component from the narrowband component, with the former used as not only a desired signal for the SPM but also as an error signal for updating the broadband sub-controller, whereas the latter adapted simultaneously to scale the auxiliary white Gaussian noise and to update the narrowband sub-controller. Extensive simulations are conducted with both the synthetic and real SPs as well as the synthetic and real noise signals that are generated by a large-scale factory cutting machine (strand-cutter) to demonstrate the advantages and effectiveness of the proposed feedforward HANC system. Comparisons are also demonstrated with the original HANC system as well as its directly extended version with an online SPM subsystem.

An active noise control system based on reference signal decomposition

The performance of the traditional active noise control system will degrade severely when the target noise has both broadband and narrowband components. At present, many scientists have discussed this topic, but the problems that certain known conditions are required or high computational complexity still exist. In This article, we propose a reference signal decomposition normalized filtered-x least mean square (RSD-NFxLMS) algorithm. By means of linear prediction (LP), the narrowband signal will be separated from the reference signal, then the broadband and narrowband signal are processed by two parallel systems respectively. Besides, we proposed a coefficients-weighting (CW) method to balance the contradiction between convergence speed and steady-state error, which significantly improves the performance of the algorithm. The simulation results show that the algorithm can achieve the same effect as Hybrid ANC (HANC) system without using known conditions, especially in low signal-to-noise ratio (SNR) and low frequency conditions.

A new feedforward and feedback hybrid active noise control system for excavator interior noise

Excavator interior noise is composed of the engine order narrowband noise and the impulsive broadband noise caused by working device. In situations where only narrowband reference signal can be obtained, the feedforward active noise control (ANC) system can just eliminate the narrowband component, failing to control the broadband noise. Hybrid feedforward and feedback ANC (HANC) systems are useful for such applications where the reference signals can be partially obtained. However, existing HANC systems have the following drawbacks: coupling between subsystems; inaccurate error and reference signals; high computational complexity; performance degradation in response to the impulsive noise. To solve the above problems, this paper proposes a new feedforward and feedback HANC system consisting of 3 subsystems, namely, a delayed feedforward narrowband subsystem, a robust feedback broadband subsystem, and a supporting error calculating (SEC) subsystem. In the proposed HANC system, not only subsystems are decoupled, but also accurate error and reference signals are provided by SEC subsystem. In addition, calculating efficiency is improved by applying the delayed notch least mean square (DLMS) algorithm to the feedforward subsystem, and the system robustness is promoted by adopting the robust algorithm into the feedback subsystem. Numerous computer simulations are performed on the excavator interior noise measured under actual operating conditions. The corresponding results demonstrate the superior performance of the proposed HANC system in terms of the power spectral density of residual error, average noise reduction, robustness of the system, and calculation efficiency to the existing HANC systems. Real-time experiments on excavator interior noise showed that the proposed HANC system was efficient in eliminating broadband and narrowband mixture noise in practice.

A novel adaptive step-size hybrid active noise control system

The conventional hybrid active noise control (HANC) system adopts the standard filtered-x least mean square (FxLMS) algorithm to adapt its control filters. However, the constant step size in the algorithm leads to not only the contradiction between convergence rate and steady-state noise reduction, but inadequate robustness under certain noise circumstances. For performance improvement, a new adaptive step-size method is incorporated into the HANC (ASHANC) system to optimize the adaptation of the filters. It combines the strengths of the variable step-size FxLMS (VSFxLMS) algorithm and the modified normalized FxLMS (MNFxLMS) algorithm. Different step-size adjustment strategies can be obtained by setting specific parameters. Furthermore, to obtain the best performance of the system, we develop a method to determine the involved key parameters on the basis of the improved particle swarm optimization (IPSO) algorithm. The objective function of the IPSO algorithm takes the convergence rate and noise reduction into consideration to search for optimum values. Simulation results demonstrate that the proposed ASHANC system achieves faster convergence rate, better noise reduction, and enhanced robustness than the other investigated systems.

A modified feedforward hybrid active noise control system for vehicle

The feedforward hybrid active noise control (HANC) system combines the strengths of the narrowband ANC (NANC) system and the broadband ANC (BANC) system. Taking this advantage into account, this paper applies it to attenuate the vehicle interior noise mixed with narrowband and broadband components. However, in the HANC system, the NANC subsystem and BANC subsystem are fed a common error signal which depends on the combined secondary signals from the both subsystems. This causes the problem of mutual coupling and hence affects the noise reduction performance. To tackle the problem, we propose a modified HANC (MHANC) system in this paper. In the MHANC system, the error signal of each ANC subsystem is independently synthesized on the basis of the estimated primary and secondary signals. Note that the NANC system for engine order noise control suffers performance deterioration when the fluctuating real-time engine speed signal is used for constructing internal reference signals. For performance improvement, an enhanced NANC (ENANC) system is developed by smoothing the fluctuating engine speed signal. Meanwhile,the ENANC system is incorporated in the MHANC system to form an enhanced MHANC (EMHANC) system. Simulations were performed on the vehicle interior noise recorded under actual driving conditions. The corresponding results demonstrate the superiority of the proposed MHANC and EMHANC systems.

A Hybrid Active Noise Control System for the Attenuation of Road Noise Inside a Vehicle Cabin.

This paper proposed a local active control method for the reduction of road noise inside a vehicle cabin. A multichannel simplified hybrid active noise control (sHANC) system was first developed and applied to the rear left seat of a large sport utility vehicle (SUV). The attenuation capability of the sHANC system was investigated through simulations, using reference signals provided by accelerometers on the suspensions and bodywork of the vehicle and microphones on the floor of cabin, respectively. It was shown that compared to the traditional feedforward system, the sHANC system using either vibrational or acoustical reference signals can produce a significant suppression of the narrowband peak noise between 75 and 80 Hz, but the system lost the control capability in a range of 100–500 Hz when the acoustic signals were used as references. To reduce the practical implementation costs while maintaining excellent reduction performance, a modified simplified hybrid ANC (msHANC) system was further proposed, in which combined vibrational and acoustical signals were used as reference signals. The off-line analyses showed that four reference accelerometers can be substituted by ten microphones without compromising attenuation performance, with 3.7 dBA overall noise reduction being achieved. The effect of delays on the reduction performance of msHANC system was also investigated. The result showed that the msHANC system was more sensitive to the delays compared to the sHANC system if using only vibrational reference signals.

Wireless-communication integrated hybrid active noise control system for infant incubators: Improve health outcomes and bonding

This research proposes to develop a wireless communication integrated hybrid active noise control (ANC) system for infant incubators. The integrated ANC system will reduce the level of noise in the infant's ear and provide two-way wireless communication between infant and his/her parents/caregivers both inside and outside the Neonatal Intensive Care Unit (NICU). The proposed system will use the ANC technique to reduce the harmful noise. The wireless communication system will be used to reduce stress and improve bonding and language development. The real-time experiments show that the proposed system can significantly reduce the noise exposure to the infants who are placed in infant incubators. Consequently, a reduction in the health risk produced by high-level noise in NICU and improved bonding opportunities for infants and their parents will be seen.

A New Hybrid Active Noise Control System with Convex Combination of Time and Frequency Domain Filtered-X LMS Algorithms

A conventional single-channel feedforward active noise control (ANC) system encounters noise from multiple sources. In many cases, there is a reference signal that is independently available which is correlated with the ambient noise. However, in some situations, a portion of the noise generated is uncorrelated with the reference signal. In this paper, a new hybrid ANC (HANC) system is proposed using a convex combination of time and frequency domain Filtered-X LMS (FXLMS) algorithms. The feedforward part uses a time domain FXLMS (TDFXLMS) algorithm to control disturbances that are correlated with the reference noise and the feedback part uses a multiresolution analysis-based frequency domain wavelet packet FXLMS (WPFXLMS) algorithm to control the uncorrelated disturbances encountered during the operation of an ANC system. An extra adaptive filter is used to smoothen the error signal in the HANC system. An effort is made to exploit the benefits of the structural design and time–frequency domain signal processing techniques for active control of disturbances that are both correlated and uncorrelated with the reference noise. As a result of the convex combination of the TDFXLMS and WPFXLMS algorithms in a HANC system, the proposed method is successful in canceling the disturbances encountered by the ANC system from multiple noise sources.

Performance evaluation of hybrid active noise control system with online secondary path modeling

A Hybrid Active Noise Control (HANC) system is used to attenuate disturbances in a scenario where a portion of noise is captured by reference sensors. In such scenarios, the secondary path continuously changes due to interference by various electrical equipment used in the Active Noise Control (ANC) system. A practical ANC system should be robust to secondary path effects. In existing literature, the secondary path used in a HANC system is estimated offline. In a real time environment, the secondary path is time varying in nature. Hence, Online Secondary Path modeling (OSPM) is a desirable addition to the design of ANC systems because it significantly improves adaptive filter convergence along with better noise reduction performance. In this paper, we propose modified HANC systems with OSPM as continuous modeling of the noise removes the secondary path effects and the HANC system can be used for real time implementation. To achieve this, we extend the OSPM technique from the Eriksson’s method to the conventional HANC system, Sun’s cascading adaptive filters algorithm and Akhtar’s HANC system. Computer simulations prove that the proposed HANC systems with OSPM improves error modeling accuracy and faster convergence against existing HANC systems where the secondary path is modeled offline. The modified HANC framework is also robust to sudden changes in the behaviour of electrical equipment while ANC operation along with providing improved noise cancelling performance.

Design and analysis of an improved hybrid active noise control system

Countering mutual coupling in the inherent structures and the non-availability of proper reference or error signals for the operation of adaptive filters has been a challenge in the design of a Hybrid active noise control (HANC) system. Existing HANC systems have not simultaneously addressed these two issues. In this paper, we propose an improved HANC system which generates most appropriate signals for operating the adaptive filters along with decoupling the inherent feedforward and feedback ANC systems in the HANC system. Here, we use an extra adaptive filter which post-processes the error signal to obtain true signals for operating the feedforward control filter which improves the convergence speed and the overall noise reduction. A Joint-Optimized Normalized Least Mean Squares algorithm is employed for generating the true signal by optimizing the system misalignment, which further improves the convergence of the adaptive filter in the feedforward part. The adaptive filter in the feedback structure also gets appropriate signals by internally generating a reference signal which is independent of the feedforward structure. A complete mathematical analysis of the proposed algorithm is done. Simulation results validate the advantages of the proposed system over its counterparts at the cost of increased computational complexity.

ハイブリッドANCシステムを用いた能動的遮音壁(ロバスト性能を確保できる適応型フィードバックANCシステムの提案及び適用)

ハイブリッドANCシステムを用いた能動的遮音壁(ロバスト性能を確保できる適応型フィードバックANCシステムの提案及び適用)

Decoupling feedforward and feedback structures in hybrid active noise control systems for uncorrelated narrowband disturbances

Hybrid feedforward and feedback structures are useful for active noise control (ANC) applications where the noise can only be partially obtained with reference sensors. The traditional method uses the secondary signals of both the feedforward and feedback structures to synthesize a reference signal for the feedback structure in the hybrid structure. However, this approach introduces coupling between the feedforward and feedback structures and parameter changes in one structure affect the other during adaptation such that the feedforward and feedback structures must be optimized simultaneously in practical ANC system design. Two methods are investigated in this paper to remove such coupling effects. One is a simplified method, which uses the error signal directly as the reference signal in the feedback structure, and the second method generates the reference signal for the feedback structure by using only the secondary signal from the feedback structure and utilizes the generated reference signal as the error signal of the feedforward structure. Because the two decoupling methods can optimize the feedforward and feedback structures separately, they provide more flexibility in the design and optimization of the adaptive filters in practical ANC applications.

ハイブリッドANCシステムを用いた能動的遮音壁(ウォーターベッド効果による増音の抑制及び各種音場における減音効果の考察)

In this paper, the hybrid active noise control (HB-ANC) system applied in the active noise barrier (ANB) is improved, and the noise attenuation performace of the ANB is invetigated under four different sound field configurations. This hybird ANB reduces the diffraction noise from top of the ANB and the noise propagated to the head position of the target person behind the ANB simultaneously to achieve higher noise attenuation. However, the waterbed effect of the feedback control part of the HB-ANC system will cause noise enhancement at some frequencies in the control area. In order to solve this problem, the HB-ANC system is improved by adding a filter to cancel the noise enhancement caused by the waterbed effect. Then, the noise attenuation performance of the hybrid ANB under four sound field configurations is evaluated by simulations. The sound field configurations are set up to investigate how the diffraction from side of the ANB and the reflection influence the performance of the ANB. An experiment in the anechoic chamber is also conducted. The results indicate that the low frequency noise attenuation can be obtained in a wide area behind the ANB, and at the head position of the person, the noise attenuation can be ensured within a wider frequency range, even for the sound fields where the uncontrolled diffraction from side and the reflection exist.

A New Time Varying Hybrid Active Noise Control System with Online Secondary Path Modelling

— Active noise control is used to reduce low frequency noises. A hybrid ANC structure combines feedforward and feedback structure to generate an anti-noise wave, which results in high performance in control of unwanted noise. In this paper, a hybrid structure for active noise control (ANC) is developed. The hybrid structure utilises a variable step size LMS algorithm for faster convergence. This structure also incorporates variable step size (VSS) online secondary path modelling, the white noise injection is stopped at the optimum point when the modelling accuracy is sufficient. Comparative simulation results shown in this paper indicate the effectiveness of the proposed approach in reducing acoustic noises.

Reply to “Comments on ‘A New Feedforward Hybrid Active Noise Control System’”

In this reply, we first provide a MATLAB program used in our simulations and clarify our claim regarding the occurrence of the so-called “firework” noise in the broadband active noise control (BANC) system. Next, we present some simulation results of the BANC using the FXLMS and the normalized FXLMS (NFXLMS) algorithms in the presence of a real noise signal generated by a large-scale rotating machine. The real noise is a mixture of several low-frequency sinusoids and a wideband noise component. The existence of “firework” noise is again confirmed in the BANC system when it is made to converge relatively fast.