Noise Control Techniques Research Articles

Analytical model of an active noise control system for performance analysis of adaptive algorithms in HVAC system

In real-world acoustic scenarios related to the problem with the low-frequency noise such as HVAC systems, the signal is a stochastic, non-stationary and time-varying process where the performance of the active noise control technique mainly depends on the characteristics of the adaptive filtering techniques. In this paper, a method for analytical modeling of active noise control of signals in MATLAB/Simulink is presented, in which the acquisition of audio signals is provided by using a National Instruments control and acquisition module. For the realization of the active noise control, an adaptive filtering system model for signal analysis has been developed, using three adaptive algorithms (LMS,RLS and NLMS). The analysis of the characteristics of each of the three investigated adaptive algorithms is performed according to four parameters: Mean Square Error (MSE), convergence speed, stability and robustness. The conclusions are presented through a comparative analysis of the results obtained from the implemented methodology. The individual characteristics and parameters that are observed for correct adaptation and optimal results of each of the adaptive filters are explained in detail.

Prediction and Control of Broadband Noise Associated with Advanced Air Mobility—A Review

This review presents an overview of advanced air mobility broadband noise (BBN) prediction and control techniques, highlighting significant advancements in various prediction models. Methods such as the semi-empirical Brooks–Pope–Marcolini (BPM) model, analytical Amiet model, and time-domain models based on the FW-H equation have been extensively studied. Machine learning (ML) shows promise in BBN prediction but requires extensive data training and application to noise source mechanisms. Passive control methods, such as leading and trailing edge serrations and blade tip designs, have been partially successful but often compromise the aerodynamic performance. Active control methods, like suction and blowing control, trim adjustments, and dielectric barrier discharge (DBD) plasma actuators, show great potential, with the latter two being particularly effective for reducing BBN in thin propeller structures. Overall, while progress has been made in understanding and predicting BBN, further research is needed to refine these methods and develop comprehensive noise control strategies. These advancements hold significant promise for effective and efficient noise mitigation in future AAM vehicles.

Enhancing active noise control through stacked autoencoders: Training strategies, comparative analysis, and evaluation with practical setup

This work is motivated by the imperative to overcome the limitations of conventional active noise control (ANC) techniques. These limitations are rooted in linear systems like the least mean square algorithm when faced with nonlinear distortions in the acoustic environment and system electronics, such as loudspeakers. This work addresses the nonlinear ANC problem by conceptualizing ANC as a deep learning problem. A novel stacked autoencoder (SAE) model is proposed, which is trained to estimate the noise that should be played at a loudspeaker so that the noise received at an error microphone may be attenuated. ANC experiments are initially set up in an anechoic room to study the fundamental performance characteristics of the architecture without extraneous considerations of room impulse response. This is followed by performance analysis in a normal reflective room. Actual noise, comprising broadband and tonal noise, is recorded in both an anechoic room and a normal reflective room. The importance of these experiments in the design process lies in their ability to account for nonlinear effects in actual setups, surpassing the limitations of relying solely on models. Experiment outcomes demonstrate that the proposed SAE model yields a noise reduction (NR) of up to 26.44 dB for wideband noise and up to 35.74 dB for tonal noise types. Additionally, there is an improvement in the extent of the quiet zone provided by the proposed SAE for tonal noise cases as compared to the traditional filtered-x least mean square (FxLMS) technique.

An Innovative Passive Noise Control Technique for Environmental Protection: An Experimental Study in Explosion Noise Attenuation

Passive noise control techniques are an effective way of mitigating environmental noise pollution caused by industrial activities, assisting with long-term sustainability in workplace health and safety. Excessive noise from various sources such as mining, construction, manufacturing, air blasting and large-scale gas and dust explosion investigations is challenging as it produces a high level of noise. Excessive explosion noise can have a significant impact on the surrounding environment and people. To suppress the noise to satisfactory levels for nearby occupants, several layers of acoustic barriers are employed. The effectiveness of each level of acoustic barrier is presented. A bottom ash granule base layer with a 300 mm thickness reduced the peak noise levels (136 dBA) by approximately 33 dBA. In the next stage, an autoclaved aerated concrete (AAC)-based 200 mm acoustic barrier was introduced, which suppressed 24 dBA of noise. The inside of the AAC acoustic barrier was finally covered with a 50 mm thick noise attenuation composite material layer constituted of a sound barrier and a sound absorber, and this composite material attenuated the noise level by 6 dBA. The entire noise suppression mechanism was found to be an effective way to suppress gas and dust explosion noise and satisfy the requirement of the occupant and sound level.

Development and Testing of an Active Noise Control System for Urban Road Traffic Noise

As urbanization accelerates, the increasing number of vehicles and travel demands contribute to escalating road traffic noise pollution. Although passive noise control techniques such as noise barriers and green belts effectively mitigate noise, they occupy urban space, exacerbating the scarcity and high cost of already congested city areas. Emerging as a novel noise reduction strategy, active noise control (ANC) eliminates the need for physical isolation structures and addresses the noise within specific frequency ranges more effectively. This paper investigates the characteristics of urban road traffic noise and develops an ANC prototype. Utilizing the Least Mean Squares (LMS) algorithm, we conduct active noise control tests for various types of single- and dual-frequency noise within the prototype’s universal platform to validate its actual noise reduction capabilities. The study demonstrates that urban road traffic noise is mostly in the mid- to low-frequency range (below 2000 Hz). The developed ANC prototype significantly reduces single- or dual-frequency noise within this range, achieving a maximum noise reduction of nearly 30 dB(A). Future research should expand noise reduction tests across more frequency bands and assess the noise reduction effectiveness against real road traffic noise.

Aerodynamics and Aeroacoustics of Leading Edge Serration in Low-Speed Axial Fans With Forward Skewed Blades

Abstract Low-speed axial fans must comply with a wide number of standards and normative restrictions, often related to the maximum noise emission levels. Among the noise control techniques in axial fans, skewed fan blades and leading edge serrations have been found to be effective in leading edge noise control, which represents one of the dominant phenomena in axial fan broadband emissions. However, these solutions are usually applied separately, and literature is scarce on systematic studies on the coupling of the two modifications. In this work, a campaign of experimental measurements was conducted on unskewed and forward-skewed axial fan blades with and without leading-edge serrations. The tests were performed in undisturbed inflow conditions. The flow field and the turbulence characteristics were measured using three-dimensional hot-wire anemometry. The suction-side sound radiation of the fans was measured with microphones in an anechoic chamber. In addition, the rotating beamforming method was used to localize the sound sources at the axial fans. It was found that, regardless of the blade skew, the leading edge serrations lead to a reduction of the sound pressure level, whereby the aerodynamic properties of the fan decrease. At the same operating points, which were achieved by adjusting the rotational speed, the sound radiation through the leading edge serrations could be reduced at high-volume flows. This effect was more pronounced with the unskewed rotor, which indicates that the positive effect of the serrations is reduced by the already optimized shape of the forward skewed fan blade. Based on the experimental results, the four geometries were further considered for numerical investigations to understand how the serrations affect the fan operations and the overall aerodynamics of the rotor. All four geometries were simulated with RANS approach at the duty point to derive a flow survey and better understand the dynamics driven by serrations and blade skewing.

Numerical Investigation on the Effect of Geometric Parameters of Chevron Nozzle on Generation of Steamwise Vortices in High Subsonic Jets

Chevron nozzle is gaining popularity as a noise control device for jet noise reduction. Though it is the only noise control technique currently in use for commercial airliners, complete design methodology of chevrons is not available. In the present work, attempt is made to understand the effect of various geometric parameters of a chevron nozzle on the jet flow using commercial RANS based CFD solvers. Enhancement in mixing, which affects the acoustic signature of the jet, can be attributed to the strength of the streamwise vortices produced by chevrons. Hence major emphasis is given on analyzing the streamwise vortices formed in the jet flow from chevron nozzle. Various geometric parameters like different number of chevrons, their length and tip angles are employed on a 30 mm diameter nozzle producing M = 0.8 jet for further investigation.

A versatile dynamic noise control framework based on computer simulation and modeling

Abstract This article attempts to effectively reduce the impact of active noise pollution on human life, and to make up for the traditional passive noise control technique. In low-frequency noise control, there are some shortcomings. The making of active noise control (ANC) technique, in low-frequency noise reduction, can achieve very good results. This article proposes a versatile dynamic noise control framework based on computer simulation and modeling. The research is mainly focused on the principle and application of versatile dynamic noise control framework. To accomplish this, a research method combining theoretical analysis, software simulation, and hardware realization is adopted. The derivation process of the adaptive algorithm (LMS algorithm, filter-XLMS algorithm, etc.) is introduced in detail, and the influencing factors of algorithm performance, a variable step size normalization algorithm based on relative error is proposed. Perform simulation calculations on various algorithms in MATLAB, analyze parameters such as step factor, filter order, etc., and the degree of influence on the algorithm’s convergence speed and steady-state performance. Common command set software is used, the path adaptive identification is realized, and the program design of the versatile dynamic noise control framework is used. After completion of software and hardware debugging on the experimental platform of generalized comfort, the experimental equipment layout is completed. Using the additive random noise method, the adaptive offline modeling of the first path of the versatile dynamic noise control framework is realized. Finally, utilizing the experimental platform of generalized comfort, the adaptive ANC experiment of the single-channel filtered least mean square algorithm is conducted, then the experimental data are analyzed, and at last, the actual application effect of the versatile dynamic noise control framework is verified.

A Review of Bionic Structures in Control of Aerodynamic Noise of Centrifugal Fans

Due to the complexity of the working conditions and the diversity of application scenarios, the normal operation of a fan, whether volute tongue, volute shell surface, or blade, often encounters some unavoidable problems, such as flow separation, wear, vibration, etc.; the aerodynamic noise caused by these problems has a significant impact on the normal operation of the fan. However, despite the use of aerodynamic acoustics to design low-noise fans or the use of sound absorption, sound insulation, and sound dissipation as the main traditional noise control techniques, they are in a state of technical bottleneck. Thus, the search for more efficient methods of noise reduction is looking toward the field of bionics. For this purpose, this paper first analyzes the mechanism of fan noise in the volute tongue and blades, and then, this paper reviews the noise control mechanism and improvement research using the bionic structures in the volute tongue structure, the contact surface of the volute shell, and the leading and trailing edges of the blade in the centrifugal fan. Finally, the current challenges and prospects of bionic structures for aerodynamic noise control of centrifugal fans are discussed.

Occupational Noise-Induced Hearing Loss in Iran: A Systematic Review and Meta-Analysis.

A large portion of Iranian Working Population (IWP) is becoming at risk of Occupational Noise-Induced Hearing Loss (ONIHL). Several primary studies have evaluated the prevalence of ONIHL in Iran with a variety of prevalence rates. We aimed to estimate the prevalence of ONIHL in the IWP using data from relevant studies. The present study is a meta-analysis and systematic review of previously published studies on ONIHL in Iran. Accordingly, the relevant articles published until Sep 1, 2021 were searched through Pub-Med, Scopus, and Google Scholar, together with Iranian scientific electronic databases. Heterogeneity between among the studies and data analysis was assessed using the I2 test and Random-Effect Model (REM) respectively. Having performed a quality assessment, the meta-analysis was performed on the data from twenty-six studies involving a total of 85685 participants. The prevalence of ONIHL was observed to range from 12.9% to 60.5% in the reviewed studies. Moreover, after combining the results from the primary research by the Random Effects Model (REM) approach, the prevalence of ONIHL among IWP was estimated to be 34.69% (95% CI: 29.10, 40.28). ONIHL is a significant concern with regard to public and occupational health in Iran. The results also highlighted the urgent need for taking appropriate preventive and control measures in the work-places; particularly by encouraging the employers and health-related policymakers to focus on preventive noise control techniques along with administrative and legislative approaches to mitigate the risk of developing ONIHL.

Recent Technological Advances in Spatial Active Noise Control Systems

This article provides a broad overview of the recent advances in the field of active noise control techniques to reduce unwanted noise over a certain spatial region of interest. By both commercial and technological advances in local active noise control systems extending the size of the quiet zone seems to be a crucial step to develop the next generation of active control systems for a more personalized and quieter audio products. In this review article, the advances over the past decade in design and development of spatial active noise control techniques to enlarge the controlled sound zone is reviewed. The focus is specifically on the adaptive control techniques and the methods proposed in the frequency domain to control the sound field. The study has paid a specific attention into the most important performance measures in designing a spatial active noise control system such as convergence rate, stability and robustness of the algorithm, and the size of quite zone and how it can be enlarged by configuring the loudspeaker and microphone array geometries. Finally, the authors will discuss the current and future challenges that should be overcome to improve the effectiveness of the recently proposed methods to expand the silence zone.

The benefits of building information modelling in construction noise control in the pre-construction phase (a focus on urban area constructions)

For inner-city construction activities, the propagated construction noise is considered the primary source of nuisance for the surrounding area. Due to the short distance between the site and neighboring buildings, passive noise control techniques such as noise barriers have a limited mitigating impact. As a result, construction companies should anticipate encountering complaints and lawsuits from residents of adjacent buildings, leading to project delays or cost overruns. Previous studies for construction noise control have primarily focused on a real-time solution such as data collection by sensors during the execution phase. Although the guidelines recommend that source management is the most effective method of controlling construction noise, there is no systematic approach for focusing on construction noise during the planning phase. Building Information Modeling (BIM) has been widely used to achieve effective project management, such as time and cost control. However, the benefits of BIM for noise-considered time planning in the pre-construction phase still need to be exploited. This research will focus on the potential of BIM for addressing construction noise as an additional factor during time planning. The findings show how multiple process plans using BIM-supported platforms can be planned and controlled to achieve the lowest risk of discomfort for neighboring area residents.

Improving the performance of an active staggered window with multiple resonant absorbers.

The active noise control (ANC) technique has been applied in staggered windows to improve the noise reduction at low frequencies. The control performance of such a system deteriorates significantly at some frequencies where the secondary source cannot radiate effectively due to the reflection at the boundaries of the staggered window. A resonant absorber consisting of a perforated panel and coiled up tubes is proposed to solve the problem. By designing a combination of different absorbers, a proper sound absorption coefficient is achieved around the ineffective frequency. Numerical simulations show that the active sound power reduction increases by 13.5 dB at the frequency with the absorbers attached on one end of the staggered window, and the overall sound power reduction between 100 and 500 Hz increases from 25.9 to 31.2 dB. Attaching the sound absorbers elsewhere in the upstream of the secondary source, for example, on the side walls of the duct also works. The active sound power reduction at 435 Hz increases by 6.3 dB after attaching the absorbers in the experiments, and the noise reduction increment at the evaluation point is 13.6 dB, which agrees with simulation results and demonstrates the feasibility of the proposed sound absorbers.

Optimization of metamaterials with complex neck shapes for aircraft cabin noise improvement

More frequently, recent low-frequency noise control techniques commonly implemented in aerospace and ground transportation as well as in building applications are based on acoustic metamaterial concepts. The technologies proposed in the literature, using layered porous materials with embedded Helmholtz resonators (HR), exhibited considerable potential when tuned at tonal, multi-tonal or narrow frequency bands. Our recent investigations have shown that the acoustical performance of these metamaterials can be further improved by the use of resonators with complex shaped necks. These necks can be designed and optimized to minimize the HR resonance frequencies (small form factor) and maximize the sound transmission loss (STL) performance. This paper presents the developed design optimization method for HRs with complex neck shapes recessed within the HR cavity. The HRs were embedded in a layer of porous material. The implemented approach was based on the transfer matrix methods (TMM) in series and in parallel coupled to a multi-objective optimization. Complex optimum neck shapes were obtained allowing for a shift towards the low frequencies of the resonator resonance with a good STL performance. Moreover the STL calculated using the TMM approach were observed to be in excellent agreement with the finite element method numerical results.

An efficient narrowband active sound profiling system with online secondary path modeling

Active noise equalization or active sound profiling techniques for sound quality enhancement tend to balance the sound pressure levels (SPLs) of certain frequency points or frequency bands of target noise to meet human perception requirements rather than simply minimizing the SPLs like active noise control (ANC) technique. Therefore, when the secondary path is time-varying, online secondary path modeling (OSPM) appears particularly important in the active sound quality enhancement systems. This paper presents a novel parallel-structure narrowband active sound profiling (NASP) system with OSPM. In the system, the OSPM subsystem uses the control signals to estimate low-order local secondary path models at the controlled frequencies instead of the usual high-order global model. This way may ensure the convergence speed and accuracy of modeling. Meanwhile, the main sound profiling subsystem employs the estimated local secondary path models to profile the targeted multi-tonal narrowband noise based on the internal model FXLMS algorithm. By using bandpass filter banks, each tonal component may be tuned relatively independently. In addition, the proposed system enjoys good profiling accuracy and stability since no additional random noise is introduced. Several simulations are provided to demonstrate the superiority of the proposed NASP system with OSPM in cancellation mode over the conventional NANC system with OSPM and evaluate the behavior of the proposed system in different time-varying scenarios. Finally, real-time experiments are also conducted to confirm the system’s ability to deal with sudden changes in the secondary path and its sound profiling capability.

Application of Hybrid Shannon's Entropy – PROMEHTEE Methods for Weighing and Prioritizing Noise Control Solutions in an Iranian Oil Refinery

Background: There have been numerous control strategies employed to prevent the very physiological and psychological impacts of noise exposure in occupational settings. The present study aims to use the Shannon's entropy – PROMEHTEE hybrid model to weigh and prioritize noise control solutions in an oil refinery. Methods: This study was performed in four stages. At first, the sound pressure levels were measured and determined according to the recommended standard of ISO 9612. Next, criteria and sound control strategies were determined using the Delphi technique. In the third stage, the weights of the criteria were determined using the Shannon's entropy method and in the last stage, the solutions were prioritized using the PROMEHTEE method. Result: According to Shannon's entropy method, criteria were sorted by the priority order of cost-effectiveness (0.2710), efficiency in reducing the noise (0.2531), executability (0.2435), safety (0.1120), process interference (0.1107) and up-to-dateness of the methods (0.091). Also, according to the PROMEHTEE method, the best solution was determined to be building a noise chamber with a weight of 0.5476, and modification or change of the work process was ranked last with a weight of -0.6905. Conclusion: The Shannon's entropy – PROMEHTEE hybrid method introduced in this study can be used as a credible scientific tool and solution to select the most appropriate noise control solution in the oil industry and other industries in which a choice of noise control technique is felt as a necessity.

NVH Analysis of Acoustic Materials by Using Aluminum and Steel metals

Sound quality evaluation has turned into a standard idea in the structure in the field of vehicle acoustic performance optimization in an endeavor to determine the issue active noise control (ANC) techniques were created where auxiliary sources were proposed to lessen the noise inside the cabin. Therefore an endeavor has been made in this paper to audit the advancements so far did in the field of optimization thinks about on decrease of noise in the truck cabins by using acoustic materials. In light of this, it is to investigate the possibility of acoustic materials as aluminum and steel metals an option with plan to improve the cabin noise by NVH analysis can be carried out by using Ansys and Hypermesh software’s. By finding the analysis values of frequency, sound and weighted sound can be concluded the acoustic materials are good for quieter applications.

Numerical simulation regarding flow-induced noise in variable cross-section pipelines based on large eddy simulations and Ffowcs Williams–Hawkings methods

Large eddy simulations and Ffowcs Williams–Hawkings acoustic analogy methods have been adopted to simulate the flow-induced noise for variable cross-section pipelines under variable flow velocity conditions in this paper, and the main influencing factors of flow-induced noise are analyzed numerically, including the flow velocity and variable diameter angle. Results manifested that the flow field distribution, sound source characteristics, and frequency spectrum characteristics of the sound pressure level (SPL) at different flow velocities follow similar trends. The average acoustic source intensity increases gradually with the increase in flow velocity. The maximum of the acoustic source intensity is located near the outlet of the variable diameter angle due to the vortex effect. The flow-induced noise in variable cross-section pipelines is mainly low-frequency noise, and its energy is mainly concentrated below 200 Hz according to the frequency spectrum characteristics. Additionally, the SPL increases with the increase in flow velocity. Compared with v = 1 m/s, the SPL at v = 2 m/s and v = 3 m/s increases by 9.4% and 22.1%, respectively. In addition, there is an approximate linearly increasing relationship between the SPL and the variable diameter angle. The minimum of the SPL appears at φ = 15.2°, and the maximum appears at φ = 25.7° at different flow velocities, which is up to 70.18 dB. Briefly, the flow-induced noise characteristics, including the average acoustic source intensity, the SPL, and the frequency spectra, are revealed in this paper. This provides a theoretical basis for the optimization of variable cross-section piping systems and the investigation of flow-induced noise control techniques.

Passive noise control in buildings: An engineering case study of ducted systems

The most common noise sources in buildings are related to Heating, Ventilating and Air Conditioning (HVAC) systems, plumbing systems, electrical systems and exterior sources. Passive Noise Control (PNC) techniques in buildings have been implemented in several ways. The aim of this work is to analyses the use of silencer to attenuate the noise in the ducts that are part of the ventilation systems in buildings, internal combustion systems, fans, gas conduction systems, boilers, etc. The main objective of a silencer is to reduce the transmission of noise, disturbing as little as possible the circulation of gas or liquid. In the first instance, the silencers are classified as reactive and dissipative, depending on whether the attenuation of the noise is produced by reflective or dissipative mechanisms, respectively. In a reactive silencer, the losses occur essentially due to the reflections of the sound waves in impedance discontinuities, such as widening or narrowing of the tube. In dissipative silencers, the flow is in contact with a large surface of absorbent material. The attenuation of the noise is then produced by visco-thermal losses in the porous material. In this work, a practical issue will be addressed with a noise reduction of 19 dBA in 60 Hz. Practical application Noise is a current issue in residential areas that could lead to health problems for people. The origin of these noises within buildings is very diverse, one of them is produced by ducts. Appling the PNC technique in modern building construction would be a good prevention practice. For this reason, in this project a PNC system was carried out in the ducts of a residential building, which could be used as a praiseworthy solution, avoiding problems for the inhabitants of these spaces.

A novel feedforward hybrid active sound quality control algorithm for both narrowband and broadband sound-profiling

Unlike the conventional active noise control (ANC) technique that aims to minimize the sound pressure level (SPL) of target noise, the active sound quality control (ASQC) technique tends to balance the SPLs of certain frequency points or frequency bands to satisfy the requirements of human perception in some applications. In this paper, a feedforward hybrid ASQC (HASQC) algorithm is proposed for the situation where both narrowband and broadband noise components reside in primary and reference noise signals. By utilizing a narrowband ASQC (NASQC) subsystem, a sinusoidal noise canceller (SNC) subsystem, and a broadband ASQC (BASQC) subsystem, the presented HASQC algorithm may control both the spectral characteristics and SPLs of the target noise with both narrowband and broadband characteristics. The algorithm inherits the advantages of existing active noise equalization or active sound profiling strategies and has greater potential to meet practical sound quality requirements. Moreover, to improve the algorithm performance, we also introduce a variable step size updating method. Extensive simulations for various scenarios are performed to demonstrate the effectiveness of the algorithm. The results show that the proposed HASQC algorithm achieves satisfactory sound quality control of the target noise in steady, dynamic as well as multi-frequency situations.