High Noise Attenuation Research Articles

The Development of a Novel Transient Signal Analysis: A Wavelet Transform Approach

This paper presents a new method for the analysis of transient signals in the frequency domain based on the Continuous Wavelet Transform (CWT). The proposed case study involves test signals measured from an electronic switch considering open and close operations. The source is connected to inductive, resistive, and capacitive loads. Resonance behaviors are introduced and compared with the Discrete Fourier Transform (DFT). Multiple factors, such as reliability, repeatability, high noise attenuation, and the smoothing of the analyzed spectrum, are considered in this study. This proposed study highlights the effectiveness of CWT in signal processing, especially in obtaining a detailed spectrum that reveals the behavior of electrical circuits. Resonance behaviors were analyzed, demonstrating that the signal processing performed by CWT is better for spectrum analysis than DFT. This study shows the potential of CWT to analyze transient electrical signals, specifically for identifying and characterizing the behavior of load connections and disconnections.

U-Net with Asymmetric Convolution Blocks for Road Traffic Noise Attenuation in Seismic Data

Road traffic noise is a special kind of high amplitude noise in seismic or acoustic data acquisition around a road network. It is a mixture of several surface waves with different dispersion and harmonic waves. Road traffic noise is mainly generated by passing vehicles on a road. The geophones near the road will record the noise while receiving the seismic signal. The amplitude of the traffic noise is much larger than the signal, which masks the effective information and degrades the quality of acquired data. At the same time, the traffic noise is coupled with the effective signal, which makes it difficult to separate them. Therefore, attenuating traffic noise is the key to improving the quality of the final processing results. In recent years, denoising methods based on convolution neural networks (CNN) have shown good performance in noise attenuation. These denoising methods can learn the potential characteristics of acquired data, thus establishing the mapping relationship between the original data and the effective signal or noise. Here, we introduce a method combining UNet networks with asymmetric convolution blocks (ACBs) for traffic noise attenuation, and the network is called the ACB-UNet. The ACB-UNet is a supervised deep learning method, which can obtain the distribution characteristics of noise and effective signal through learning the training data and then effectively separate the two to achieve noise removal. To validate the performance of the proposed method, we apply it to synthetic and real data. The data tests show that the ACB-UNet can obtain good results for high amplitude noise attenuation and is practical and efficient.

Accelerated dispersion curve calculations for periodic vibro-acoustic structures

Over the years, metamaterials have shown their potential in a wide range of different disciplines, e.g. optics, electromagnetics, dynamics etc. Metamaterials are, often periodic, engineered structures made of conventional materials but which exhibit properties not encountered in nature. In the field of noise and vibration, metamaterials have received increasing interest since they can obtain frequency ranges of high noise and vibration attenuation, called stop bands. Their performance is often investigated by means of dispersion curves, which are calculated based on a single unit cell and assuming a structure of infinite periodic extent. Nowadays, the attenuation of acoustic and structural waves is commonly tackled as two separate problems, whereby either acoustic or structural dispersion curves are used. Recently, vibro-acoustic unit cell designs have come to the fore which can exhibit appealing characteristics, such as simultaneous structural and acoustic stop bands. To consider the vibro-acoustic coupling in these unit cell designs during the performance predictions, vibro-acoustic dispersion curve calculations are thus required. However, these computations are typically cumbersome to perform due to the associated high computational cost and therefore, often, uncoupled dispersion curves are used during the performance assessment. Although several unit cell model order reduction approaches have recently been proposed to accelerate the dispersion curve computations, such as the Bloch mode synthesis (BMS) and Generalized Bloch mode synthesis (GBMS), they are not readily applicable to vibro-acoustic unit cells. To accelerate vibro-acoustic dispersion curve calculations, this work extends the BMS and GBMS techniques towards 2D and 3D periodic vibro-acoustic systems. To balance accuracy versus speed, the extended BMS reduction basis is constructed using a split set of vibro-acoustic coupled modes, while the extended GBMS reduction basis uses the uncoupled modes. Several verification cases demonstrate that strongly accelerated vibro-acoustic dispersion curve computations are achieved whereby the vibro-acoustic coupling inside the unit cell is accurately accounted for.

Parametric Optimization of Local Resonant Sonic Crystals Window on Noise Attenuation by Using Taguchi Method and ANOVA Analysis

Local resonant sonic crystals (LRSCs) window as a novel design has recently been proposed to achieve a good balance between noise mitigation, natural ventilation and natural lighting. In an effort to explore the feasibilities of such designs in civil residential buildings, an optimization methodology was proposed to develop a more compact LRSCs window with high noise attenuation performance in the present study. Specifically, the Taguchi method was adopted for the design of experiments on the parameters of interest and their corresponding levels, and SN ratio analysis was then applied for the parametric evaluations on the noise attenuation on specified frequencies in traffic noise (concentrated sound energy frequency range: 630–1000 Hz). Three optimal sets of design parameters on the interested frequencies, namely, 630 Hz, 800 Hz and 1000 Hz were obtained. ANOVA analysis was conducted to quantificationally identify the design parameters with statistical significance and remarkable contribution to the desired performance. Results indicate that the slit size has the most significant influence on the overall noise attenuation performance, followed by cavity width. An optimal set of design parameters to achieve the overall best noise reduction performance in the frequency range of 630–1000 Hz was finally determined by combining the SN ratio and ANOVA analysis. A prototype of the final optimized LRSCs window was then fabricated and tested in a semi-anechoic chamber. Good agreement was found between the experiment and numerical simulation. In comparison to the benchmark case, the final optimized design can achieve a further noise reduction by 2.84 dBA, 3.48 dBA and 5.56 dBA for the frequencies of 630 Hz, 800 Hz and 1000 Hz, respectively. The overall noise reduction for the interested frequency range can be promoted by 3.28 dBA. The results indicate that the proposed optimization methodology is practical and efficient in designing a high-performance LRSCs window or improving similar applications.

Evaluation of noise barriers based on geometries and materials: a review.

The acoustical properties of a barrier are highly dependent on the physical properties of the material and the internal structure of the material. The acoustical material can curtail the quality of sound or enhance the dispersion, depending on the application being considered. The efficient acoustic performance of noise barriers possessing different shapes and materials including waste materials is reviewed for field implementation to achieve the low-cost sustainable noise barrier application in the Indian context. The review analysis of research papers demonstrates that the acoustic performance of barriers is dependent on different shapes, materials, and textures as well as onsite geometry. Based on the review study, T-shaped barriers with a soft top surface are found to be efficient at noise attenuation. For transparent barriers, perceived loudness and noise annoyance are assessed lower than that for opaque barriers and utilization of waste materials viz. plastic, rubber, bottom coal ash, etc. gives high noise attenuation along with low-cost efficiency. Noise pollution levels are high from prescribed noise limits in most of the Indian metropolitan cities. The Indian government is working on mitigation strategies of noise pollution as well as abiding laws regarding noise standards for the zone (residential, industrial, commercial, and silences) wise. In contrast, some communities which are adjacent to roads are suffering from high noise levels in the ambience. Therefore, it requires a coherent strategy for long-term measures intended at minimizing exposure of noise hence providing much more comfort to live, work, and shop near high-traffic roads. Noise barriers are highly beneficial in mitigating the emitted noise from the traffic.

Semi-adaptive active noise cancellation headphones

Active noise cancellation (ANC) headphones are becoming increasingly important as they can effectively attenuate perceived ambient noise. Fixed filters are commonly applied in commercially available ANC headphones due to their robustness. However, they are not capable of adapting to changes that occur in dynamic environments, resulting in degraded ANC performance. In contrast, adaptive filters are able to update the ANC filters to compensate for noise in dynamic environments, but large estimation errors can occur due to a sudden change in direction/type of noise or secondary path. Some studies have suggested an ANC system by combining fixed and adaptive filters. Based on this mechanism, we propose a semi-adaptive ANC system in which the fixed and adaptive filters are weighted in real-time. Initially, the weighting for the fixed filter dominates the whole system to ensure the robustness of the ANC system. Then, the residual error provided by the adaptive filter is simulated and compared to the real measured one to determine the relative weighting between the fixed and adaptive filters. In this study, this approach is applied to a feedback ANC system. Simulation results show that our proposed approach achieves high noise attenuation performance while maintaining robustness with time-varying secondary paths.

MODEL-ORIENTED METHOD OF DESIGN IMPLEMENTATION WHEN CREATING DIGITAL FILTERS

This article discusses the example of model-oriented method of design and development of digital low-pass filters (LPF) for automatic control systems (ACS). Typically, high frequency noise and disturbance attenuation is carried out by analogue LPF. However, technical implementation of analogue filters higher than the second order arouse certain difficulties related with the need of precise passive components ratings selection (resistors, capacitors). If the noise and disturbances spectral composition is known, it is possible to build digital LPF with the Nyquist frequency greater than the maximum frequency in the noise spectrum. Such possibility has appeared because of cheap, energy-efficient, high-speed 32-bit microcontrollers market entry. They have analogue signals sampling rate of 30 kHz and above. The traditional approach using the “manual” method of filter parameters calculation, obtaining their recurrence expressions and further program implementation requires high qualification and a lot of time consumption from the developer. An alternative to this approach is the model-oriented method of design (MOMD) in MatLab environment when in the one environment the design of digital LPF, verificaton of its performance as a part of the ACS, generation and compilation of program codes for selected microcontroller family take place. MOMD can also be used in the designs of bandpass and bandstop filters for adaptive control systems or systems of technical diagnostics. If during the commissioning or the operation of ACS there is a need in digital LPF parameters change then this operation can be performed within half an hour. MOMD technology allows to significantly reduce the time for developing a specific product without loss of quality in its design ‘cause of extensive possibilities of MatLab development environment.

Analytical and Parametric Optimization of Force Transmissibility by Taguchi Method for Double Stage Engine Mountings

It is essential to design a warship to avoid detection by submarines or enemy ships. One of the recent techniques used is to mount all vibrant machinery on a double stage vibration isolation system. For high structure-borne noise attenuation there is requirement of two-stage mounting system. The main goal of current research work is to reduce vibration levels from machinery to foundation, and thereby to reduce radiate noise levels from ship hull. The present work deals with the mathematical modeling and parametric optimization of force transmissibility (Ftr) for design of engine foundation system. The vertical vibrations of the system are assumed to be most predominant, and other types of vibrations are neglected. The research work is carried out for finding parameters of mounts and optimizing the same. The analysis is based on discrete system modeling. Taguchi method is used for finding optimal combination of process parameters based on S/N ratio and analysis of variance (ANOVA) is statistical technique to investigate contribution of each process parameters on the performance characteristic. The result shows that spring stiffness is most affecting process parameter.

Modified PID control with H∞ loop shaping synthesis for RO desalination plants

This paper deals with the PID control synthesis with robust (H∞) loop shaping framework to manage MIMO reverse osmosis (RO) desalination plants. This new method takes advantage of the robust controller which has a fixed low order of conventional PID scheme guaranteeing robust stability and performance under large parametric uncertainties, external disturbances, and sensor noises. The coprime factor uncertainty description in H∞ loop shaping methodology can cover a wide variety of uncertainties over all frequencies for the RO plants. The test results demonstrate that the achieved controller has high stability margin, showing disturbance and noise attenuation abilities. Furthermore, most interactions between control channels have been decoupled in the complete control system. The presented control approach can help reduce membrane cleaning, save energy, and reduce product water costs for the RO plants. Note that weather changes increase unstableness in RO plants but the water treatment facilities are only dimensioned for PID control. In addition, this study addresses control robustness as well as performance of a RO system against uncertainties, disturbances, and noises. Finally, the present control method can be utilized for efficiently controlling water quality (including quantity) and managing water facility of the RO desalination plants.

Noise reduction in urban LRT networks by combining track based solutions

The overall objective of the Quiet-Track project is to provide step-changing track based noise mitigation and maintenance schemes for railway rolling noise in LRT (Light Rail Transit) networks. WP 4 in particular focuses on the combination of existing track based solutions to yield a global performance of at least 6dB(A). The validation was carried out using a track section in the network of Athens Metro Line 1 with an existing outside concrete slab track (RHEDA track) where high airborne rolling noise was observed. The procedure for the selection of mitigation measures is based on numerical simulations, combining WRNOISE and IMMI software tools for noise prediction with experimental determination of the required track and vehicle parameters (e.g., rail and wheel roughness). The availability of a detailed rolling noise calculation procedure allows for detailed designing of measures and of ranking individual measures. It achieves this by including the modelling of the wheel/rail source intensity and of the noise propagation with the ability to evaluate the effect of modifications at source level (e.g., grinding, rail dampers, wheel dampers, change in resiliency of wheels and/or rail fixation) and of modifications in the propagation path (absorption at the track base, noise barriers, screening). A relevant combination of existing solutions was selected in the function of the simulation results. Three distinct existing solutions were designed in detail aiming at a high rolling noise attenuation and not affecting the normal operation of the metro system: Action 1: implementation of sound absorbing precast elements (panel type) on the track bed, Action 2: implementation of an absorbing noise barrier with a height of 1.10–1.20m above rail level, and Action 3: installation of rail dampers. The selected solutions were implemented on site and the global performance was measured step by step for comparison with simulations.

Comparing three-dimensional Bayesian segmentations for images with low signal-to-noise ratio (SNR<1) and strong attenuation

This paper examines three Bayesian statistical segmentation techniques with an innovative attenuation compensation on synthetic data and breast ultrasound medical images. All use expectation maximization for estimating the Gaussian model parameters and segment the data using a three-dimensional (3-D) Markov random field pixel neighborhood. This paper compares three Bayesian segmentation techniques: maximum a posteriori simulated annealing (MAP-SA), MAP iterated conditional modes (MAP-ICM), and maximization of posterior marginals (MPM). We conclude that because of the high speckle noise and adverse attenuation challenges of breast ultrasound, the MPM algorithm has the best performance. This is due to better localized segmentation than the other MAP techniques. We present results first with synthetic images then with breast ultrasound. Our new contributions for a 3-D breast ultrasound produce improved results using a model of the noise, in which the Gaussian mean is proportional to the image attenuation with depth, combined with a new prior probability model.

Time–frequency domain SNR estimation and its application in seismic data processing

Abstract Based on an approach estimating frequency domain signal-to-noise ratio (FSNR), we propose a method to evaluate time–frequency domain signal-to-noise ratio (TFSNR). This method adopts short-time Fourier transform (STFT) to estimate instantaneous power spectrum of signal and noise, and thus uses their ratio to compute TFSNR. Unlike FSNR describing the variation of SNR with frequency only, TFSNR depicts the variation of SNR with time and frequency, and thus better handles non-stationary seismic data. By considering TFSNR, we develop methods to improve the effects of inverse Q filtering and high frequency noise attenuation in seismic data processing. Inverse Q filtering considering TFSNR can better solve the problem of amplitude amplification of noise. The high frequency noise attenuation method considering TFSNR, different from other de-noising methods, distinguishes and suppresses noise using an explicit criterion. Examples of synthetic and real seismic data illustrate the correctness and effectiveness of the proposed methods.

Performance and Robustness Considerations for Tuning of Proportional Integral/Proportional Integral Derivative Controllers with Two Input Filters

The aim of this work is to present an extension of the closed-loop model-reference robust tuning (MoReRT) methodology to proportional integral and proportional integral derivative control algorithms enhanced with two input filters (set-point and feedback signal filters) for control of stable, integrating, inverse response, and unstable controlled processes. The method is based on the use of target models that include two design parameters (closed-loop dominant poles relative speed and damping). The control system performance/robustness trade-off is analyzed to reduce the design parameters to only one directly related with the control system robustness measured with the maximum sensitivity (MS). The proposed design methodology takes into consideration the control system load-disturbance rejection, set-point tracking, control effort smoothness, measurement of high frequency noise attenuation, and robustness to changes on the controlled process dynamics. The incorporation of these two input filters allows ta...

Feedback active noise control in a crew rest compartment

Active systems for noise cancelation are typically used to reduce low frequency noise (below 500 Hz). In this study, a method to reduce the delay in the control loop of feedback noise control systems is discussed. There are certain applications in which we may choose to control a specific frequency range; hence, a selection of the control-band must be performed. This selection is commonly done with analog filters introducing delay in the signal path. However, in feedback systems, the reference signal is calculated from the error signal which makes their performance more sensitive to these delays. In this contribution, the filtered-error feedback filtered-reference LMS algorithm (FE-FBFxLMS) is analyzed. Consequently, control-band selection is performed in an auxiliary loop removing the additional delay required in the signal path. This method of band selection also allows a reduction of the delay due to the anti-aliasing filters by using faster low-order filters in terms of group delay. With this delay reduction, higher noise attenuation is expected at the cost of a slower convergence rate. This method is applied to control broadband noise in a single channel feedback system in simulation and experiment.

Digital Active EMI Control Technique for Switch Mode Power Converters

A novel electromagnetic interference (EMI) suppression technique based on field programmable logic array technology is proposed to provide a significant EMI noise attenuation for switch-mode power converters. This technique uses noise acquisition at very high-sampling rate. The noise signal is processed to invert its phase angle and reconstructed with high fidelity to counteract the noise signal before reaching the line impedance stabilization network. Thus, high noise attenuation is achieved. The new technique is validated through simulation and experimental results of a single-phase ac-dc converter. The proposed technique can be extended to dc/dc converters to replace the conventional passive EMI filter where the PCB space is restricted. This technique can be a desired contingent in industrial applications where space is a major design constraint.

Design of a feedback controller for active noise control with in-ear headphones

Nowadays mobility is an important factor in many jobs. Therefore, there is an increased use of planes, trains and cars, and the associated exposure to noise. Good acoustic insulation is often hard to realize due to the involved extra weight. Ear protection or headphones with active noise control (ANC) may be a possible solution. Today circumaural and supra-aural ANC headphones with good attenuation are commercially available. However, their weight and the necessary headband can impair the wearing comfort. ANC in-ear headphones do not have these disadvantages and, therefore, there is a need of further research in the field of ANC. In ANC headphones, disturbing noise is minimized by an out-of-phase anti-noise. Therefore, the noise is recorded by microphones next to each ear, and filtered by an analog or digital platform to generate the anti-noise. There are two main control strategies depending on the position of the microphones, feedforward control with an external reference microphone and feedback control with an internal error microphone. The presentation will focus on the design of feedback controllers and the main problem regarded to in-ear headphones, interpersonal variances, which make the design of stable controllers with high noise attenuation difficult. A model-based solution will be presented.

Signal subspace approach for psychoacoustically motivated speech enhancement

In this paper we deal with the perceptually motivated signal subspace methods for speech enhancement. We focus on extended spectral-domain-constrained (SDC) estimator. It is obtained using Lagrange multipliers method. We present an algorithm for a precise computation of the Lagrange multipliers, allowing for a direct shaping the residual noise power spectrum. In addition the SDC estimator is presented in a new, possibly more effective form. As a practical implementation of the estimator we propose perceptually constrained signal subspace (PCSS) method for speech enhancement. The approach utilizes masking phenomena for residual noise shaping and is optimal for the case of coloured noise. Also, less demanding approximate version of this method is derived. Finally comparative evaluation of the most known subspace-based methods is performed using objective speech quality measures and listening tests. Results show that the PCSS method outperforms other methods providing high noise attenuation and better speech quality.

Earplug Actuator Selection for a Miniature Personal Active Hearing Protection System

AbstractThere are many industrial environments which are exposed to a high-level noise. It is necessary to protect people from the noise. Most of the time, the consumer requires a miniature version of a noise canceller to satisfy the internal working place requirements. Very important thing is to select the most appropriate personal hearing protection device, for example an earplug. It should guarantee high passive noise attenuation and allow for secondary sound generation in case of active control. In many cases the noise is nonstationary. For instance, some of the noisy devices are switched on and off, speed of some rotors or fans changes, etc. To avoid any severe transient acoustic effects due to potential convergence problems of adaptive systems, a fixed-parameter approach to control is appreciated. If the noise were stationary, it would be possible to design an optimal control filter minimising variance of the signal being the effect of the acoustic noise and the secondary sound interference. Because of noise nonstationarity for most applications, the idea of generalised disturbance defined by a frequency window of different types has been developed by the authors and announced in previous publications. The aim of this paper is to apply such an approach to different earplugs and verify its noise reduction properties. Simulation experiments are conducted based on real world measurements performed using the G. R. A. S. artificial head equipped with an artificial mechanical ear, and the noise recorded in a power plant.

Using a small-scale reverberation chamber to improve a ship's double sandwich panel noise attenuation performance

Regulations now require passenger ships to have low noise levels in accommodation spaces. Complex structural wall panels such as a double sandwich panels are often used to provide the required high noise attenuation. However, because of their complex structures, the prediction and improvement of the sound transmission loss (STL) of these panels often can not be achieved only with theoretical approaches. In this paper, an experimental approach using a small-scale reverberation chamber is applied to improve the STL of a double sandwich panel for installment in a ship. Firstly, a small-scale reverberation chamber is set up. For test chamber qualification, the STLs of a thin plate, a commercial ship's sandwich panel and a high noise attenuation panel are measured and compared with those tested in a large-scale reverberation chamber and those calculated by the transfer matrix method (TMM). Secondly, the small-scale reverberation chamber is used to analyze the STL of a double sandwich panel in terms of the influences of the inside perforate plates and air gap thickness on attenuation. In order to improve the attenuation performance of the double sandwich panel, the STLs of test specimens with various materials between sandwich panels are measured and compared. Finally, the panel with the highest noise attenuation is proposed and verified using the large-scale reverberation chamber

Multiple input–multiple output adaptive feedback control strategies for the active headrest system: design and real‐time implementation

AbstractIn this article, multiple input–multiple output adaptive feedback control techniques for acoustic noise control in a headrest system are developed. The main goal underlying their design is to provide acoustic comfort to the user, i.e. high noise attenuation level over possibly large areas at the ears. Classical Internal Model Control system does not yield acceptable performance. An approach based on estimates of the residual noise at the ears is then proposed. It is shown that increase in the number of secondary sources to operate for one channel improves the performance. The experiments of tonal noise control are performed on an originally set‐up prototype of the active headrest system. The results obtained are illustrated in the promoted form of distribution of zones of quiet. Copyright © 2003 John Wiley & Sons, Ltd.