Adaptive Feedback Active Noise Control Research Articles

Robust parallel virtual sensing method for feedback active noise control in a headrest

Additional filter method (AFM) and remote microphone method (RMM) are the two common virtual sensing methods used to compensate for active noise control (ANC) in headrest systems where mounting the error microphone at the desired zone is inconvenient. AFM and RMM are divided into two stages: the training and control stages. In the training stage, a temporary microphone is installed at the target to generate the additional and observation filters for AFM and RMM, respectively. However, they are fully effective only when the disturbances are consistent during both the training and control stages. To solve this dilemma, we propose a robust parallel virtual sensing method (PVSM) for multichannel adaptive feedback ANC system to attenuate the varying narrowband noises. During the training stage, the potential primary noises are used to model a group of parallel additional filters. Subsequently, the synthetic observation filter required for estimating the virtual error signal is derived using minimax optimisation. In the control stage, the most eligible additional filter that minimises the energy of the estimated virtual error signal is matched per frame based on the minimum-mean-square-estimated-error-matching mechanism and applied to the adaptive controller. Theoretical analysis validates that when the primary source varies, PVSM is more robust than both AFM and RMM, and performs noise reduction similar to the direct control with the temporary error microphone placed at the target. The proposed PVSM is further analysed in terms of its convergence condition and computational complexity. Numerous simulations and real-time experiments conducted using a dual-channel ANC headrest validate the feasibility of the proposed algorithm and present a guideline for the selection of frame length in PVSM. Therefore, the proposed PVSM can be considered a robust virtual sensing method against varying primary disturbances.

Integrated active noise control for open-fit hearing aids with customized filter

The open-fit hearing aids that allow air and sound into the ear canal have become popular in recent years. Unfortunately, they result in the noise leakage problem that bypasses the hearing aids toward the eardrum and will degrade the quality of desired signal. This paper proposes a modified audio-integrated adaptive feedback active noise control (ANC) system for open-fit hearing aids. Traditionally, the ANC system attenuates the total power of the unwanted noise over the entire spectrum. To increase efficiency and save power consumption of hearing aids, we design a customized filter based on the hearing threshold of hearing-impaired patient to generate the anti-noise only in audible frequency range. The performance of the proposed method is verified by both computer simulations and real-time experiments.

Robust and Adaptive Feedback Noise Attenuation in Ducts

In this brief, the attenuation of sound propagation in an air-handling duct using robust and adaptive feedback active noise control (ANC) strategies is investigated. The case of multiple narrow-band disturbances located in distinct frequency regions and the interference occurring in the presence of disturbances with very close frequencies are considered. The active control uses a loudspeaker as a compensatory system. The objective is to minimize the residual noise at the end of the duct segment considered. The system does not use any additional sensors for receiving real-time information upon the disturbances. This brief illustrates the application of the techniques for active vibration control presented by Landau et al. to this problem. A hierarchical feedback control approach will be used. At the first level, a robust linear controller will be designed taking advantage of the knowledge of the domains of variation of the frequencies of the noise disturbances. To further improve the performance, a direct adaptive control algorithm will be added. Its design is based on the use of the internal model principle combined with the Youla–Kucera parameterization of the controller. Guidelines for the design of the baseline (central) controller are provided. Both robust and adaptive controls require the knowledge of the discrete-time model of the compensation path, which is obtained by identification from experimental data. Experimental results on a relevant duct ANC test bench will illustrate the performance of the proposed methodology.

Active control of wind turbine noise using audio integrated pillows

This paper presents integration of active noise control (ANC) system with auditory masking technique to cancel wind turbine noises on pillows and improve sleep quality. By using recorded wind turbine noise, the broadband feedforward and the adaptive feedback ANC algorithms are developed to conduct experiments in real-time. Experimental results show that the feedforward ANC systems reach better performance than the feedback ANC system, and the auditory masking technique can be effectively integrated with the ANC algorithms to mask the residual noise. The generated quiet zone can cover the pillow to support free head movement.

Performance analysis of an adaptive feedback active noise control based earmuffs system

This paper analyzes the performance of the adaptive feedback active noise control (FBANC) based earmuffs system. The system’s noise reduction performance is obtained in a closed-form equation with respect to two top-level design constraining parameters, i.e., secondary path delay and noise bandwidth. To derive the equation, we utilize a simplified and equivalent linear prediction ANC model and parameterize noise bandwidth using an autoregressive model. The derived equation is validated by simulations and experimental tests performed for the ANC earmuff system. The high degrees of noise reduction, which are 14.9dB for the airplane noise and 20.4dB for the house heater noise, obtained from the experimental tests confirm the feasibility of the ANC earmuffs application.

Adaptive feedback active noise control using wavelet frames: simulation and experimental results

Two strategies for adaptive feedback active noise control (ANC) systems are presented here based on wavelet frames. In the first strategy, the noise at the cancellation point is estimated and used as the reference signal in the feedforward ANC system. In the second strategy only the error signal is utilized in the wavelet-based ANC system. The advantages of the second method are: simple structure and less computational load (no need to estimate noise) as well as less sensitivity to the accuracy of estimated secondary path filter. Its disadvantage is high sensitivity to learning rate. To treat this, an adaptive learning rate is proposed to maintain the stability and convergence rate simultaneously. Simulations are carried out for typical linear/nonlinear cases to compare the proposed methods with FxLMS and neural network-based ANC algorithms. Experiments are then conducted to evaluate the developed algorithms. Results show the superior performance of proposed methods in terms of the convergence rate and noise attenuation especially in the presence of an inaccurate identified secondary path filter.

Parallel feedback active noise control of MRI acoustic noise with signal decomposition using hybrid RLS-NLMS adaptive algorithms.

This paper presents a cost-effective adaptive feedback Active Noise Control (FANC) method for controlling functional Magnetic Resonance Imaging (fMRI) acoustic noise by decomposing it into dominant periodic components and residual random components. Periodicity of fMRI acoustic noise is exploited by using linear prediction (LP) filtering to achieve signal decomposition. A hybrid combination of adaptive filters-Recursive Least Squares (RLS) and Normalized Least Mean Squares (NLMS) are then used to effectively control each component separately. Performance of the proposed FANC system is analyzed and Noise attenuation levels (NAL) up to 32.27 dB obtained by simulation are presented which confirm the effectiveness of the proposed FANC method.

A simplified adaptive feedback active noise control system

In the adaptive feedback active noise control system based on the internal model control (IMC) structure, the reference signal is regenerated by synthesizing the error signal and the secondary signal filtered with the estimation of the secondary path, hence more computation load and extra programming are required. Motivated by the engineering truth that the primary noise cannot be completely cancelled in most practical active noise control applications and the error signal still contains some portions of the primary noise, a simplified adaptive feedback active noise control system is proposed in this paper, which adopts the error signal directly as the reference signal in an adaptive feedforward control system and utilizes the leaky filtered-x LMS algorithm to update the controller. The convergence properties of the proposed system are investigated and its advantages are discussed by comparing with other feedback control systems as well as the weakness. Finally, simulations and experiments are carried out to demonstrate the effectiveness of the proposed system.

Adaptive Feedback Active Noise Control for Yacht Environments

In a yacht cabin, high-quality absorbing materials can reduce in a good way medium and high-frequency noises, but they are completely inefficient in the case of low-frequency noises. In this brief, a detailed analysis of low-frequency noises in a yacht environment is presented; several boat conditions, depending on the presence of different noise sources (e.g., air conditioning, engines) and various navigation velocities are investigated. In this context, a specific multichannel feedback active noise control system, derived from the well-known filtered-x approach, is designed and installed in a bedroom of a yacht in order to reduce the acoustical annoyance using four error microphones and two sub-woofers for antinoise generation. The results of practical experiments are shown in order to demonstrate the effectiveness of the proposed system.

Prediction filter design for active noise cancellation headphones

Digital active noise control (ANC) for headphones usually has to predict the noise because of the latency of common audio converters. In adaptive feedback ANC, the prediction is based on the noise that entered the headphone. This noise is low-pass filtered because of the physical barrier of the ear cups. In this study, this low-pass characteristic is exploited to define a prediction filter which does not require real-time updates. For broadband noises, the prediction filter performs better than adaptive prediction methods like the least mean squares algorithm or iterated one-step predictions in the relevant frequency band. This is shown in simulations as well as in measurements. In addition, the authors show that their prediction filter is more robust against changes in the acoustics of the headphone.

Adaptive Narrowband ANC, Design and Implementation Issues

This paper presents the design and implementation of an adaptive feedback Active Noise Control (ANC) to cancel the low frequency narrowband noise remaining inside a headset shell. The implementation issues were addressed and tested on a commercial fixed point Digital Signal Processor (DSP).

Adaptive Active Noise Control Schemes for Headset Applications

Abstract This paper presents the design and implementation of adaptive feedback active noise control system (ANC) for head phone applications. Active Noise Control is a technique of acoustic noise reduction using a secondary source of sound which produces “antinoise” to cancel the primary noise. In this paper, narrow band single channel feedback ANC for headsets application is focused upon. The filter weights are updated by using the feedback form of Filtered-X LMS (FXLMS) algorithm. Performances for the IIR-based filter, FIR-based filter are compared with those of the algorithm by using ADALINE. The real time implementation of the system is performed using TMS320C6713 DSP Starter Kit (DSK) and the performance is analyzed for two tone sinusoidal noise.

Active noise control system for headphone applications

This paper presents the design and implementation of an adaptive feedback active noise control (ANC) system for headphone applications. The ideal position of the error microphone in the ear-cup was studied and determined experimentally, and music signals were used for adaptive system identification of the secondary path. The designed ANC headphone was implemented using the TMS320C32 digital signal processor for real-time experiments. Performance has been evaluated and compared with a high-end commercial ANC headphone using the same set of primary noises including real-world engine noises. Experiment results show the proposed ANC headphone achieves higher noise cancellation, especially for low-frequency harmonics.

Adaptive feedback active noise control headset: implementation, evaluation and its extensions

In this paper, we present design and real-time implementation of a single-channel adaptive feedback active noise control (AFANC) headset for audio and communication applications. Several important design and implementation considerations, such as the ideal position of error microphone, training signal used, selection of adaptive algorithms and structures will be addressed in this paper. Real-time measurements and comparisons are also carried out with the latest commercial headset to evaluate its performance. In addition, several new extensions to the AFANC headset are described and evaluated.

A Recursive Deconvolution Approach to Disturbance Reduction

Active noise control (ANC) uses an estimate of the noise affecting a system in order to remove its effect from the output. In some applications, it is possible to directly measure the noise and a feedforward compensator can be used. Other applications require instead that the noise be estimated from its effect on the system. This results in an adaptive feedback ANC, see a previous paper by Gan and Kuo. The identification of the disturbance from the output of the linear system is a deconvolution problem. In this paper, we study a deconvolution technique for the active reduction of the influence of the disturbance on the output of a linear control system. The regulator that we present does not affect the behavior of the system in the absence of disturbances.

Applications of adaptive feedback active noise control system

This paper presents the experimental results of using the single-channel adaptive feedback active noise control (AFANC) algorithm with an innovative setup to achieve global attenuation of industrial machine noise in settings such as large manufacturing plants. An effective solution of using active/passive techniques and three distributed error sensors is proposed. The performance of the AFANC algorithm is verified by real-time experiments using the TMS320C32 DSP to control vibratory bowl and welding power generator noises. The experiments results show that this single-channel AFANC system can effectively reduce the noise level and is cost effective, portable, and easy for installation to control many noisy sources in large spaces.

An integrated audio and active noise control headset

This paper presents an integrated approach in designing a noise reduction headset for audio and communication applications. Conventional passive headsets give good attenuation of ambient noise in the upper frequency range, while most of these devices fail below 500 Hz. Unlike the feedforward method, the adaptive feedback active noise control technique provides more accurate noise cancellation since the microphone is placed inside the ear-cup of the headset. Furthermore, the system uses a single microphone per ear cup, thus producing a more compact, lower power consumption, cheaper solution and ease of integration with existing audio and communication devices to form an integrated feedback active noise control headset. Simulation results have been conducted to show that the integrated approach can remove the disturbing noise and, at the same time, allow the desired speech or audio signal to pass through without cancellation.