Papers by Keyword: Active Noise Control

Abstract: A hybrid active-passive noise control system for a HVAC duct combines both a physicalnoise absorber and an active system. Due to the presence of the passive component, requirements forthe active system can be relaxed, removing the need for detecting and suppressing noise in the frequencyrange already covered by the passive elements. A typical noise measurement system adaptedto working in airflow usually uses a microphone with a housing designed to reduce the noise generateddue to local turbulent flow introduced by the housing itself. Alternatively, there are microphonesspecifically designed to work in the airflow.During work on the hybrid active-passive noise control system both a microphone designed forairflow and a microphone with special housing were tested. While these solutions can be used forresearch, both have issues making them impractical when designing a commercial product. This, alongwith the required narrow frequency range motivated the authors to consider vibration measurementsperformed by appropriately installed accelerometers. An audio signal is then synthesized using thosemeasurements and it is confronted with signals obtained at the same time with microphones.In the paper the proposed method is presented and validated with a laboratory HVAC installation ofa large cross-section and an originally designed passive absorber. Obtained results encourage further research.

Abstract: An active noise-canceling casing is very attractive for reduction of sound generated bydevices. Such casing can provide good noise reduction for low frequencies, where a passive barrierwould be too thick for practical use. The classical active noise control approach, where the goal is tominimize the sound pressure level around multiple microphones outside the casing can be used. However,it requires placing external microphones, what makes the overall technical solution not acceptedfor many applications. The active vibration control, where the goal is to minimize vibrations of allplates, requires only sensors on the plates. However, in this solution, in turn, noise reduction resultsare worse. This paper presents employment of the idea of the virtual microphone-based approach toimprove results from the system based on vibration sensors only, which are used to estimate acousticpressure at specific locations in the acoustic field. By using a two-stage structure, the system is tunedto reconstruct the same vibrations of the plates, which were present when the acoustic pressure wereminimized directly in the square sense. A laboratory active noise-canceling casing used for experimentsis made of 5 actively controlled aluminum plates mounted on a steel frame. It is passivelyisolated from the floor. On each plate, three electrodynamical actuators are installed. The controlsystem is experimentally verified and obtained results are reported.

Abstract: This paper presents a method for the active noise and vibration control (ANC/AVC) of harmonically related nonstationary disturbances using varying-sampling-time linear parameter-varying (LPV) controller. The frequencies are assumed to be known and varying within given ranges and they are multiples of one fundamental frequency.

Abstract: The idea of active casing is an approach to reduce device and machinery noise by controlling vibration of casing walls. The sound insulation efficiency of this technique for a single-plate casing was confirmed by the authors in previous publications. However, under specific circumstances, a dedicated double-panel structure can yield even higher noise reduction. The aim of this paper is to propose and evaluate by means of laboratory experiments the performance of a double-panel casing in comparison with a single-panel casing. An adaptive control strategy based on the Least Mean Square (LMS) algorithm is used to update control filter parameters. A low-frequency noise in the range up to 250 Hz is considered. Obtained results are reported, discussed, and conclusions for future research are drawn.

Abstract: The aim of this paper is to present a method of nonparametric and parametric secondary path model identification for adaptive active noise control systems with low-power non-Gaussian excitations of the form of a higher-order discrete-time multisine random process and data processing based on cross-higher-order spectra. Properties of the discussed method are illustrated by simulation experiments devoted to secondary path identification for feedforward and feedback active noise control systems. Its robustness to nonlinear distortions implied by data acquisition system and adaptation procedure is proved.

Abstract: An active casing made of appropriately controlled vibrating plates can be used to reduce noise propagating from the mechanism enclosed in the casing. Since a practical vibrating casing can behave in a nonlinear way, the performance quality strongly depends on the ability of control filters to compensate for the nonlinearity. The classical approach to nonlinear active control, e.g. based on the Volterra filters, can deal with harmonics generated by the nonlinearity. However, when a complex structure is considered, neural networks have a higher potential. Although, they are much more computationally demanding, for some cases they can be simplified and still provide acceptable performance.In this paper, results of control obtained for a real casing with multiple actuators exciting each wall are presented and discussed.

Abstract: In order to solve the hazards of indoor low-frequency noise on the human body, the low-frequency noise reduction system is designed for a confined space by using the active control theory, and the process of adaptive noise elimination is achieved through the FX-LMS algorithm. The system hardware is integrated with the sound sensor, the complex programmable logic devices, the digital to analog converter and micro control unit to build the core circuit. Furthermore, the processing software of noise reduction is implemented by the FXLMS. Through the system test, the result shows that the noise reduction system can effectively reduce the low frequency noise intensity in the confined space.

Abstract: According to the vehicle interior low frequency noise existing, vehicle interior adaptive active noise control strategy is established based on the FXLMS algorithm, designed the core circuit module active noise controller, including the vehicle interior noise signal amplification module, a main control unit, audio power amplifier module and power module, completed development of the controller hardware, and programming the control software system; using this system, on vehicle driving conditions vice driver left ear position low frequency noise cancellation control in the steady state, the 8.5 dB (Lin) and 10.2dB (Lin) the amount of noise reduction.

Abstract: Noise affect people’s all kinds of activities widely, such as sleep and rest, damage to the hearing, and even cause the nervous system, cardiovascular system, digestive system diseases. In practice, we often encounter pulse signals that are extremely harmful to human body health. In this paper, active noise control of symmetric α stable (SαS) distribution impulsive noise is studied. The algorithm based on the nonlinear transformation is proposed. Compared to the previous algorithm, it does not need the parameter selection and thresholds estimation. Results prove the effectiveness of the algorithm.

Abstract: The commercial feasibility of active noise control (ANC) is very promising due to its capability beyond passive noise control (PNC). To some extent ANC becomes a complement of PNC. The active noise reduction is also capable and beneficial in reducing noise selectively. However, the active noise reduction using a conventional secondary source can become very complicated if a significant noise level reduction is required, since a large number of secondary sources will be needed. The active noise reduction is also less effective for reducing high-frequency noise. With such perspectives, a novel approach has been developed using a multipole secondary source to addressthe problems mentioned. In addition, the multipole secondary source will be used for numerical simulation of noise reduction in of propeller noise source in a free field.