scholarly journals An Evaluation of Active Noise Control in a Cylindrical Shell

1989 ◽  
Vol 111 (3) ◽  
pp. 337-342 ◽  
Author(s):  
R. J. Silcox ◽  
H. C. Lester ◽  
S. B. Abler
Keyword(s):  
Cylindrical Shell ◽  
Analytical Model ◽  
Noise Control ◽  
Active Noise Control ◽  
Effective Control ◽  
Elastic Cylindrical Shell ◽  
Noise Sources ◽  
Active Noise ◽  
Fixed Array ◽  
Forced Responses

This paper examines the physical mechanisms governing the use of active noise control in an extended volume of a cylindrical shell. Measured data were compared with computed results from a previously derived analytical model based on infinite shell theory. For both the analytical model and experiment, the radiation of external monopoles is coupled to the internal acoustic field through the radial displacement of the thin, elastic, cylindrical shell. An active noise control system was implemented inside the cylinder using a fixed array of discrete monopole sources, all of which lie in the plane of the exterior noise sources. Good agreement between measurement and prediction was obtained for both internal pressure response and overall noise reduction. Attenuations in the source plane greater than 15 dB were recorded along with a uniformly quieted noise environment over an indicative length inside the experimental model. Results indicate that for forced responses with extended axial distributions, axial arrays of control sources may be required. Finally, the Nyquist criteria for the number of azimuthal control sources is shown to provide for effective control over the full cylinder cross section.

scholarly journals Multichannel Feedforward Active Noise Control System with Optimal Reference Microphone SelectorBased on Time Difference of Arrival

2018 ◽  
Vol 8 (11) ◽  
pp. 2291 ◽  
Author(s):  
Kenta Iwai ◽  
Satoru Hase ◽  
Yoshinobu Kajikawa
Keyword(s):  
Noise Control ◽  
Acoustic Noise ◽  
Control Point ◽  
Active Noise Control ◽  
Broadband Noise ◽  
Time Difference ◽  
Arrival Direction ◽  
Noise Sources ◽  
Time Difference Of Arrival ◽  
Active Noise

In this paper, we propose a multichannel active noise control (ANC) system with an optimal reference microphone selector based on the time difference of arrival (TDOA). A multichannel feedforward ANC system using upstream reference signals can reduce various noises such as broadband noise by arranging reference microphones close to noise sources. However, the noise reduction performance of an ANC system degrades when the noise environment changes, such as the arrival direction. This is because some reference microphones do not satisfy the causality constraint that the unwanted noise propagates to the control point faster than the anti-noise used to cancel the unwanted noise. To solve this problem, we propose a multichannel ANC system with an optimal reference microphone selector. This selector chooses the reference microphones that satisfy the causality constraint based on the TDOA. Some experimental results demonstrate that the proposed system can choose the optimal reference microphones and effectively reduce unwanted acoustic noise.

A Review of Active Noise Control Applications on Noise Barrier in Three-Dimensional/Open Space: Myths and Challenges

2019 ◽  
Vol 18 (04) ◽  
pp. 1930002 ◽  
Author(s):  
Hsiao Mun Lee ◽  
Zhaomeng Wang ◽  
Kian Meng Lim ◽  
Heow Pueh Lee
Keyword(s):  
Open Space ◽  
Noise Control ◽  
Active Noise Control ◽  
Three Dimensional ◽  
Construction Site ◽  
Noise Sources ◽  
Current State ◽  
Active Noise ◽  
Noise Barrier ◽  
Passive Noise

Active noise control (ANC), with counteracting sound in exact equal magnitude and opposite phase to the noise to be controlled, is often considered as a potential solution for solving complex noise problems. However, there are both myths and challenges in its implementations. In a crowded city like Singapore, many noise sources from construction site and subway track are located very close to the residential and commercial buildings. It was suggested by few researchers that by placing suitable control speakers at the construction site (working principle of ANC), the noise from the construction site could be prevented from propagating to the surrounding buildings. Similarly, for viaduct or subway track, by placing control speakers along the viaduct or track, the noise generated by the passing trains or vehicles could be reduced based on the principle of ANC technique. However, implementation of ANC technique on these noise issues is not easy as all of these noise control problems involve multiple noise sources with complex or transient frequency spectrum in large three-dimensional/open space. Therefore, the main intention of the present paper is to discuss the current state of the art of this topic as well as to examine the potential application and limitation of the ANC technique in mitigating unwanted noise, particularly in large three-dimensional/open space and with cooperation of passive noise barrier.

scholarly journals An adaptive algorithm, based on modified tanh non-linearity and fractional processing, for impulsive active noise control systems

2017 ◽  
Vol 37 (3) ◽  
pp. 495-508 ◽  
Author(s):  
Muhammad T Akhtar
Keyword(s):  
Adaptive Algorithm ◽  
Noise Control ◽  
Active Noise Control ◽  
Main Idea ◽  
Nonlinear Process ◽  
Order Moment ◽  
Least Mean Square ◽  
Noise Sources ◽  
Active Noise ◽  
Gradient Computation

This paper presents an adaptive algorithm for active control of noise sources that are of impulsive nature. The impulsive type sources can be better modeled as a stable distribution than the Gaussian. However, for stable distributions, the variance (second order moment) is infinite. The standard adaptive filtering algorithms, which are based on minimizing variance and assuming Gaussian distribution, converge slowly or become even unstable for stable (impulsive) processes. In order to improve the performance of the standard filtered-x least mean square (FxLMS)-based impulsive active noise control (IANC) systems, we propose two enhancements in this paper. First, we propose employing modified tanh function-based nonlinear process in the reference and error paths of the standard FxLMS algorithm. The main idea is to automatically give an appropriate weight to the various samples in the process, i.e. appropriately threshold the very large values so that system remains stable, and give more weight to samples below threshold limit so that the convergence speed can be improved. A second proposal is to incorporate the fractional-gradient computation in the update vector of IANC adaptive filter. Computer simulations have been carried out using experimental data for the acoustic paths. The simulation results demonstrate that the proposed algorithm is very effective for IANC systems.

scholarly journals Active Noise Control with a Single Nonlinear Control Filter for a Vibrating Plate with Multiple Actuators

2013 ◽  
Vol 38 (4) ◽  
pp. 537-545 ◽  
Author(s):  
Krzysztof Mazur ◽  
Marek Pawełczyk
Keyword(s):  
Nonlinear Control ◽  
Noise Control ◽  
Active Noise Control ◽  
Effective Control ◽  
Destructive Interference ◽  
Linear Filters ◽  
Secondary Sources ◽  
Active Noise ◽  
Vibrating Plates ◽  
Multiple Actuators

Abstract Vibrating plates can be used in Active Noise Control (ANC) applications as active barriers or as secondary sources replacing classical loudspeakers. The system with vibrating plates, especially when nonlinear MFC actuators are used, is nonlinear. The nonlinearity in the system reduces performance of classical feedforward ANC with linear control filters systems, because they cannot cope with harmonics generated by the nonlinearity. The performance of the ANC system can be improved by using nonlinear control filters, such as Artificial Neural Networks or Volterra filters. However, when multiple actuators are mounted on a single plate, which is a common practice to provide effective control of more vibration modes, each actuator should be driven by a dedicated nonlinear control filter. This significantly increases computational complexity of the control algorithm, because adaptation of nonlinear control filters is much more computationally demanding than adaptation of linear FIR filters. This paper presents an ANC system with multiple actuators, which are driven with a single nonlinear filter. To avoid destructive interference of vibrations generated by different actuators the control signal is filtered by appropriate separate linear filters. The control system is experimentally verified and obtained results are reported.

Implementation of coherence-based-selection multi-channel wireless Active Noise Control in headphone

2021 ◽  
Vol 263 (4) ◽  
pp. 1945-1953
Author(s):  
Xiaoyi Shen ◽  
Dongyuan Shi ◽  
Woon-Seng Gan ◽  
Santi Peksi
Keyword(s):  
Numerical Simulations ◽  
Noise Reduction ◽  
Noise Control ◽  
Noise Source ◽  
Reference Signal ◽  
Active Noise Control ◽  
Selection Algorithm ◽  
Noise Sources ◽  
Active Noise ◽  
Reference Signals

Active noise control (ANC) headphone is widely used to attenuate the noise around human' s ear. The microphone mounted on the conventional ANC headphones collected the mixed reference signals when more than one noise sources are often present in the surrounding. In this case, the uncorrelated noise sources involved in the mixed reference usually deteriorate the noise reduction performance of the ANC headphones. To solve this problem, wireless microphones are proposed to install close to each potential noise source in the environment. The microphones pick up the clean reference signals and transmit them to the ANC controller embedded in the headphones with time-advance wirelessly. Every reference signal selected by a coherence-based-selection algorithm is provided individual control filter in each ear. Each control filter updated by using a single clean reference offers better noise reduction performance for ANC headphones. Furthermore, numerical simulations and real-time experiment results in this paper demonstrate the improvement of the proposed method compared with conventional ANC headphones.

scholarly journals AUTOMOBILE INTERNAL COMBUSTION ENGINE LOW FREQUENCY NOISE REDUCTION USING ACTIVE NOISE CONTROL SOLUTIONS

Akustika ◽  
2019 ◽  
Vol 34 ◽  
pp. 113-117 ◽  
Author(s):  
Andrey Vasilyev
Keyword(s):  
Internal Combustion Engine ◽  
Noise Reduction ◽  
Noise Control ◽  
Combustion Engine ◽  
Active Noise Control ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Sources ◽  
Active Noise

Increased level of automobile low-frequency noise may cause significant environmental pollution, driver and passenger discomfort etc. For automobile equipped with internal combustion engine forming of either internal or external noise is mainly caused by engine operation. Approaches to automobile low-frequency noise reduction are suggested using active noise control method. The different variants of principal schemes and constructions of electronic units of forming required vibroacoustic characteristic of active noise control system were developed by the author either for complex noise reduction of experimental unit or for investigation of the separate noise sources reduction. Intercommunication of engine compartment and passenger compartment and coherent low-frequency sound radiation by air-suctioning pipe and exhaust pipe are taking into consideration. Construction of active noise control unit designed by author for complex reduction of exhaust and intake engine low-frequency noise is described. The results described in this paper may be useful for further development and application of constructions of active noise control systems as for efficient complex engine noise reduction or for reduction of the separate automobile engine noise sources.

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