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"Noise control"
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Noise-controlling casings
\"Noise-Controlling Casings offers a range of feasible noise-controlling strategies for different kinds of devices generating excessive noise. Depending on the required performance and the availability of energy sources, three solution categories are presented: passive (no external energy is needed, but performance is limited), semi-active (little energy is needed, but performance achieves higher values) and active (best performance, but an external energy source is needed). Two very important benefits of these proposed solutions are global noise reduction (in an entire enclosure or the surrounding space) and compact technology (contrary to other active noise control solutions requiring a large number of secondary sources and distributed sensors). Many of the solutions presented are original approaches by the authors, their own developed concepts and new elements and designs that have gained recognition in prestigious journals. The book provides a theoretical background to the research, looking at system configurations, mathematical modelling, signal processing implementation and numerical analysis. The proposed ideas can be applied to any devices provided they have casings of thin walls or they can be enclosed by casings of thin walls. Applications include industrial devices, household appliances, vehicle or aircraft cabins and more. This book will be of interest to professionals and students in the fields of acoustics, vibration, signal processing, control, automotive and aircraft engineering.\"--Publisher marketing.
Book
Adaptive Filtered-x Least Mean Square Algorithm to Improve the Performance of Multi-Channel Noise Control Systems
This paper proposes an optimized control filter (OCF) based on the Filtered-x Least Mean Square (FxLMS) algorithm for multi-channel active noise control (ANC) systems. The proposed OCF-McFxLMS algorithm delivers three key contributions. Firstly, even in difficult noise situations such as White Gaussian, Brownian, and pink noise, it greatly reduces error, reaching nearly zero mean squared error (MSE) values across all Microphone (Mic) channels. Secondly, it improves computational efficiency by drastically reducing execution time from 58.17 s in the standard McFxLMS algorithm to just 0.0436 s under White Gaussian noise, enabling real-time noise control without compromising accuracy. Finally, the OCF-McFxLMS demonstrates robust noise attenuation, achieving signal-to-noise ratio (SNR) values of 137.41 dB under White Gaussian noise and over 100 dB for Brownian and pink noise, consistently outperforming traditional approaches. These contributions collectively establish the OCF-McFxLMS algorithm as an efficient and effective solution for real-time ANC systems, delivering superior noise reduction and computational speed performance across diverse noise environments.
Journal Article
Sound-politics in São Paulo
\"Cardoso presents Sound-Politics in São Paulo as the first book-length treatment on controversies surrounding noise control in Latin America\"-- Provided by publisher.
Book
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.
Journal Article
Incubator-based Sound Attenuation: Active Noise Control In A Simulated Clinical Environment
Noise in the neonatal intensive care unit can be detrimental to the health of the hospitalized infant. Means of reducing that noise include staff training, warning lights, and ear coverings, all of which have had limited success. Single family rooms, while an improvement, also expose the hospitalized infant to the same device alarms and mechanical noises found in open bay units. We evaluated a non-contact incubator-based active noise control device (Neoasis[TM], Invictus Medical, San Antonio, Texas) in a simulated neonatal intensive care unit (NICU) setting to determine whether it could effectively reduce the noise exposure of infants within an incubator. In the NICU simulation center, we generated a series of clinically appropriate sound sequences with bedside medical devices such as a patient monitor and fluid infusion devices, hospital air handling systems, and device mechanical sounds. A microphone-equipped infant mannequin was oriented within an incubator. Measurements were made with the microphones with the Neoasis[TM] deactivated and activated. The active noise control device decreased sound pressure levels for certain alarm sounds by as much as 14.4 dB (a 5.2-fold reduction in sound pressure) at the alarm tone's primary frequency. Frequencies below the 2 kHz octave band were more effectively attenuated than frequencies at or above the 2 kHz octave band. Background noise levels below 40 dBA were essentially not impacted by the active noise control device. The active noise control device further reduces noise inside infant incubators. Device safety and potential health benefits of the quieter environment should be verified in a clinical setting.
Journal Article
Active noise control of a supersonic underexpanded planar jet guided by resolvent analysis
This study is dedicated to achieving efficient active noise control in a supersonic underexpanded planar jet, utilizing control parameters informed by resolvent analysis. The baseline supersonic underexpanded jet exhibits complex wave structures and substantial high-amplitude noise radiations. To perform the active control, unsteady blowing and suction are applied along the nozzle inner wall close to the exit. Employing both standard and acoustic resolvent analyses, a suitable frequency and spanwise wavenumber range for the blowing and suction is identified. Within this range, the control forcing can be significantly amplified in the near field, effectively altering the original sound-producing energetic structure while minimizing far-field amplification to prevent excessive noise. A series of large-eddy simulations are further conducted to validate the control efficiency, demonstrating an over 10 dB reduction in upstream-propagated screech noise. It is identified that the present unsteady control proves more effective than steady control at the same momentum coefficient. The controlled jet flow indicates that the shock structures become more stable, and the stronger the streamwise amplification of the forcing, the more likely it is to modify the mean flow characteristics, which is beneficial for reducing far-field noise radiation. Spectral proper orthogonal decomposition analysis of the controlled flow confirms that the control redistributes energy to higher forcing frequencies and suppresses large-scale antisymmetric and symmetric modes related to screech and its harmonics. The findings of this study highlight the potential of resolvent-guided control techniques in reducing noise in supersonic underexpanded jets and provide a detailed understanding of the inherent mechanisms for effective noise reduction through active control strategies.
Journal Article
Optimizing active noise control for acoustic calibration: influence of algorithm and control speaker distance
A controlled environment with minimal background noise is required for acoustic calibration procedures. To meet this requirement, an active noise control system was developed and implemented for semi-reverberant or real-world acoustic settings to create a small, localized quiet zone. This study compares two adaptive algorithms, Least Mean Squares and Filtered-x Least Mean Squares. The effectiveness of each method is evaluated based on the reduction of the noise signal. The result shows that the Least Mean Squares method is easier to implement, but with limited attenuation, the maximum reduction is 6 dB at 250 Hz. In contrast, the Filtered-x Least Mean Squares method provides a better noise reduction with more than 10 dB attenuation at several frequency bands. In addition, the influence of different spacing between the control speaker and the error microphone is also assessed. Results from the experiment indicate that a 15 cm spacing between them is best suited for this specific setup, with attenuation peaks exceeding 10 dB.
Journal Article
Spline Adaptive Filtering Algorithm-based Generalized Maximum Correntropy and its Application to Nonlinear Active Noise Control
This study proposes a spline filtering algorithm-based generalized maximum correntropy criterion (GMCC), named the spline adaptive filter (SAF-)-GMCC algorithm. Compared with traditional spline algorithms, the SAF-GMCC can cope with impulsive interference effectively, because the GMCC has a low sensitivity to mutation signals. The GMCC-based variable step-size spline filtering algorithm (SAF-GMCC) is proposed to solve the limitation of the fixed step-size on the SAF-GMCC algorithm’s performance and to improve the convergence rate and steady-state error performance. Combining these algorithms with the active noise control (ANC) model, this study proposes the filtered-c generalized maximum correntropy criterion (FcGMCC) and variable step-size filtered-c generalized maximum correntropy criterion (FcVGMCC) algorithms. Finally, the nonlinear system identification model simulates an experimental environment with impulsive interference. The SAF-GMCC and SAF-VGMCC algorithms offer better robustness than the existing algorithms. And the alpha-stable noise environment simulation with different impact strengths, in the ANC model verifies the FcGMCC and FcVGMCC algorithms’ robustness in nonlinear and non-Gaussian noise environments.
Journal Article