Sen M. Kuo

A secondary path modeling technique for active noise control systems

A secondary path modeling technique for active noise control systems is developed for both on-line and off-line modeling with faster convergence and higher modeling accuracy. The optimum delay for the adaptive prediction error filter to reduce the interference in system modeling is equal to the length of the impulse response of the secondary path being modeled.

RESIDUAL NOISE SHAPING TECHNIQUE FOR ACTIVE NOISE CONTROL SYSTEMS

An active noise control system attenuates the overall sound field. However, in some applications, it is desirable to change the spectral contents of the residual noise. In this Letter, a residual noise spectrum shaping technique based on the filtered‐E least‐mean‐square algorithm has been developed. This technique can be applied to active noise control of one‐dimensional ducts and three‐dimensional enclosures, for both narrow‐band and broadband noises. Computer simulations demonstrate that this method not only attenuates the noise level, but also effectively reshapes the spectrum of the residual 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

Recent advances on active noise control : open issues and innovative applications

The problem of acoustic noise is becoming increasingly serious with the growing use of industrial and medical equipment, appliances, and consumer electronics. Active noise control (ANC), based on the principle of superposition, was developed in the early 20th century to help reduce noise. However, ANC is still not widely used owing to the effectiveness of control algorithms, and to the physical and economical constraints of practical applications. In this paper, we briefly introduce some fundamental ANC algorithms and theoretical analyses, and focus on recent advances on signal processing algorithms, implementation techniques, challenges for innovative applications, and open issues for further research and development of ANC systems.

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.

Nonlinear adaptive bilinear filters for active noise control systems

The reference and error channels of active noise control (ANC) systems may be saturated in real-world applications if the noise level exceeds the dynamic range of the electronic devices. This nonlinear saturation degrades the performance of ANC systems that use linear adaptive filters with the filtered-X least-mean-square (FXLMS) algorithm. This paper derives a bilinear FXLMS algorithm for nonlinear adaptive filters to solve the problems of signal saturation and other nonlinear distortions that occur in ANC systems used for practical applications. The performance of this bilinear adaptive filter is evaluated in terms of convergence speed, residual noise in steady state, and the computational complexity for different filter lengths. Computer simulations verify that the nonlinear adaptive filter with the associated bilinear FXLMS algorithm is more effective in reducing saturation effects in ANC systems than a linear filter and a nonlinear Volterra filter with the FXLMS algorithm.

A robust hybrid feedback active noise cancellation headset

This paper investigates the robustness of a hybrid analog/digital feedback active noise cancellation (ANC) headset system. The digital ANC systems with the filtered-x least-mean-square (FXLMS) algorithm require accurate estimation of the secondary path for the stability and convergence of the algorithm. This demands a great challenge for the ANC headset design because the secondary path may fluctuate dramatically such as when the user adjusts the position of the ear-cup. In this paper, we analytically show that adding an analog feedback loop into the digital ANC systems can effectively reduce the plant fluctuation, thus achieving a more robust system. The method for designing the analog controller is highlighted. A practical hybrid analog/digital feedback ANC headset has been built and used to conduct experiments, and the experimental results show that the hybrid headset system is more robust under large plant fluctuation, and has achieved satisfactory noise cancellation for both narrowband and broadband noises.

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.

Development and analysis of an adaptive noise equalizer

The paper presents the development and analysis of a narrowband adaptive noise equalizer (ANE), which can either amplify or attenuate narrowband noise. The output of the ANE system contains residual narrowband components, the amplitudes of which can be linearly and arbitrarily controlled by adjusting the gain parameter of the equalizer, thus providing the desired noise shaping capability. The characteristics of the ANE system are analyzed and applied to active noise control. >

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.