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13 pages, 11752 KiB

Open AccessArticle

Active Sidewall Panels with Virtual Microphones for Aircraft Interior Noise Reduction

by Malte Misol

Appl. Sci. 2020, 10(19), 6828; https://0-doi-org.brum.beds.ac.uk/10.3390/app10196828 - 29 Sep 2020

Cited by 8 | Viewed by 2441

This work deals with the reduction of aircraft interior noise using active sidewall panels (linings). Research work done in the past showed that considerable reductions of the sound pressure level (SPL) in the cabin are possible using structural actuators mounted on the lining [...] Read more.

This work deals with the reduction of aircraft interior noise using active sidewall panels (linings). Research work done in the past showed that considerable reductions of the sound pressure level (SPL) in the cabin are possible using structural actuators mounted on the lining and error microphones distributed in front of the linings. However, microphones are undesirable for error sensing because they are not suitable for the realisation of an integrated and autonomous active lining (smart lining module). Therefore, the goal of the present work is the replacement of the microphones by structural sensors. Using the structural sensors as remote sensors in combination with an acoustic filter, virtual microphones can be defined. The present study relies on experimental data of a double-walled fuselage system which is mounted in a sound transmission loss facility. Simulation results based on measured time data and identified frequency response functions are provided. Different configurations of virtual microphones are investigated regarding the SPL reduction and the induced vibration of the lining panel. Full article

(This article belongs to the Special Issue Noise Barriers)

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12 pages, 4210 KiB

Open AccessArticle

Active Control of Low-Frequency Noise through a Single Top-Hung Window in a Full-Sized Room

by Bhan Lam, Dongyuan Shi, Valiantsin Belyi, Shulin Wen, Woon-Seng Gan, Kelvin Li and Irene Lee

Appl. Sci. 2020, 10(19), 6817; https://0-doi-org.brum.beds.ac.uk/10.3390/app10196817 - 29 Sep 2020

Cited by 16 | Viewed by 3108

Abstract

The push for greater urban sustainability has increased the urgency of the search for noise mitigation solutions that allow for natural ventilation into buildings. Although a viable active noise control (ANC) solution with up to 10 dB of global attenuation between 100 Hz [...] Read more.

The push for greater urban sustainability has increased the urgency of the search for noise mitigation solutions that allow for natural ventilation into buildings. Although a viable active noise control (ANC) solution with up to 10 dB of global attenuation between 100 Hz and 1000 Hz was previously developed for an open window, it had limited low-frequency performance below 300 Hz, owing to the small loudspeakers used. To improve the low-frequency attenuation, four passive radiator-based speakers were affixed around the opening of a top-hung ventilation window. The active control performance between 100 Hz and 700 Hz on a single top-hung window in a full-sized mock-up apartment room was examined. Active attenuation came close to the performance of the passive insulation provided by fully closing the window for expressway traffic and motorbike passing noise types. For a jet aircraft flyby, the performance of active attenuation with the window fully opened was similar to that of passive insulation with fully closed windows. In the case of low-frequency compressor noise, active attenuation’s performance was significantly better than the passive insulation. Overall, between 8 dB and 12 dB of active attenuation was achieved directly in front of the window opening, and up to 10.5 dB of attenuation was achieved across the entire room. Full article

(This article belongs to the Special Issue Noise Barriers)

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17 pages, 3321 KiB

Open AccessArticle

Suitability of Active Noise Barriers for Construction Sites

by Shahin Sohrabi, Teresa Pàmies Gómez and Jordi Romeu Garbí

Appl. Sci. 2020, 10(18), 6160; https://0-doi-org.brum.beds.ac.uk/10.3390/app10186160 - 04 Sep 2020

Cited by 13 | Viewed by 2916

Abstract

Barriers are increasingly used to protect the pedestrian and neighboring buildings from construction noise activities. This study aims to investigate the suitability of applying active noise control on barriers in a construction site to protect the street area and neighboring buildings. Transducers that [...] Read more.

Barriers are increasingly used to protect the pedestrian and neighboring buildings from construction noise activities. This study aims to investigate the suitability of applying active noise control on barriers in a construction site to protect the street area and neighboring buildings. Transducers that are simulated in this work are close to the barrier, and their optimal positions are defined in such a way that the control system has the maximum performance at the neighboring areas close to the construction sites. To begin with, the suitable location of the control sources is found when the total squared pressure is minimized at the positions of noise receivers. The suitable location of the error sensors is, then, found when the control sources are fixed at the position of the previous step and the total squared pressure is minimized at the error sensors. The best location for the error sensors is defined when the maximum reduction is achieved in the target area. It is observed that suitable positions for the transducers depend on the location of target areas for noise control, the position of the noise source, and its operating frequency. In this investigation, a unique configuration is proposed for the transducers that achieves a comparable reduction both at the street area and the neighboring buildings, simultaneously. The results show that the active noise barrier with a height of 2.5 m can achieve an extra insertion loss in the street zone, varies from 9.3 to 16.4 dB (in comparison with passive noise barrier) when the distance of the noise source from the barrier changes in the range of 7 to 1 m, respectively. Those values are of the same order for the passive noise attenuation. Furthermore, similar results are achieved when attempting to cancel the shadow zone of a façade 15 m away from the barrier. Full article

(This article belongs to the Special Issue Noise Barriers)

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12 pages, 4103 KiB

Open AccessArticle

Effects of the Top Edge Impedance on Sound Barrier Diffraction

by Xiaofan Huang, Haishan Zou and Xiaojun Qiu

Appl. Sci. 2020, 10(17), 6042; https://0-doi-org.brum.beds.ac.uk/10.3390/app10176042 - 31 Aug 2020

Cited by 9 | Viewed by 2884

Abstract

Sound barriers can be configured with different top edge impedance to improve their noise control performance. In this paper, the integral equation method was used to calculate the sound field of a barrier with various top edge impedance, and the effects of the [...] Read more.

Sound barriers can be configured with different top edge impedance to improve their noise control performance. In this paper, the integral equation method was used to calculate the sound field of a barrier with various top edge impedance, and the effects of the barrier top edge impedance on sound barrier diffraction were investigated. The simulation results showed that the noise reduction performance of a sound barrier with a soft boundary on its top edge was larger than that with a hard boundary, but there were some impedance values which, if assigned to the top edge boundary, would give the sound barrier even better noise reduction performance. It was found that the sound barrier with a good top edge impedance formed a dipole-like radiation pattern above the barrier to expand the effective range of the shadow zone. The research discoveries reported in this paper point out the potentials of using acoustics metamaterials or active control methods to implement the desired good impedance on the top edge of a sound barrier for better noise reduction. Full article

(This article belongs to the Special Issue Noise Barriers)

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25 pages, 10456 KiB

Open AccessArticle

Traffic Noise Mitigation Using Single and Double Barrier Caps of Different Shapes for an Extended Frequency Range

by Domingo Pardo-Quiles, José-Víctor Rodríguez, Jose-Maria Molina-García-Pardo and Leandro Juan-Llácer

Appl. Sci. 2020, 10(17), 5746; https://0-doi-org.brum.beds.ac.uk/10.3390/app10175746 - 19 Aug 2020

Cited by 6 | Viewed by 2303

Abstract

The primary function of noise barriers is to shield inhabitants of affected areas from excessive noise generated by road traffic. To enhance the performance of noise barriers while simultaneously adhering to height restrictions, the attachment of structures (caps) of different shapes to the [...] Read more.

The primary function of noise barriers is to shield inhabitants of affected areas from excessive noise generated by road traffic. To enhance the performance of noise barriers while simultaneously adhering to height restrictions, the attachment of structures (caps) of different shapes to the tops of conventional screens can be considered. These caps can significantly impact the diffracted sound energy, thereby increasing the desired global acoustic losses. This work presents a comprehensive study of the acoustic performance of noise barriers with single and double attached caps of different shapes through a calculation of their insertion losses (IL). This study comprehensively addresses and compares different types, sizes, combinations, and numbers of noise barrier caps for different scenarios (including sloping and absorbent grounds) and sources (“car” and “ambulance”) for an extended frequency band up to 10 kHz. To the best of the authors’ knowledge, this is a range that has not previously been analyzed. A variety of different cap shapes were considered including cylinders, rectangles, trapezoids, and Y/T-shaped forms. To calculate the IL, an innovative and fast uniform theory of diffraction (UTD)-based method developed by the authors was applied in all simulations. The results showed that the Y-shaped single and double barrier caps were, in general, the most effective at increasing IL without raising the height of the barrier, thereby successfully managing the aesthetic impact. The results also showed how the consideration of sloping and absorbent floors could also contribute to improved noise abatement. Full article

(This article belongs to the Special Issue Noise Barriers)

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20 pages, 4066 KiB

Open AccessArticle

Notes on a New Structure of Active Noise Control Systems

by Jarosław Figwer and Małgorzata I. Michalczyk

Appl. Sci. 2020, 10(14), 4705; https://0-doi-org.brum.beds.ac.uk/10.3390/app10144705 - 08 Jul 2020

Cited by 2 | Viewed by 2005

Abstract

The idea of active noise control is an attenuation of unwanted noise with an additionally generated acoustic wave using the phenomenon of interference. Its technical realization employs advanced control algorithms. Active noise control is an area of intense research and practical engineering applications. [...] Read more.

The idea of active noise control is an attenuation of unwanted noise with an additionally generated acoustic wave using the phenomenon of interference. Its technical realization employs advanced control algorithms. Active noise control is an area of intense research and practical engineering applications. In the paper a new structure of adaptive active noise control systems is proposed. Compared with classical control systems used for active noise control, the proposed structure contains in an error signal measurement path an additional discrete-time filter that estimates signal values at the input of this path. These estimates are then used to tune the corresponding adaptive filter. Properties of the proposed adaptive active noise control structure are illustrated by simulation examples in which a feedforward control system equipped with this additional filter is used to attenuate unwanted wide-sense stationary random noises with continuous and mixed spectra. Full article

(This article belongs to the Special Issue Noise Barriers)

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18 pages, 8879 KiB

Open AccessArticle

Application of Soundproofing Materials for Noise Reduction in Dental CAD/CAM Milling Machines

by Eun-Sung Song, Young-Jun Lim, Joongsoo Lee, Jung-Bon Moon and Bongju Kim

Appl. Sci. 2020, 10(8), 2768; https://0-doi-org.brum.beds.ac.uk/10.3390/app10082768 - 16 Apr 2020

Cited by 4 | Viewed by 3822

Abstract

Soundproofing materials are widely used in various fields as a passive measure to reduce noise. Despite this, there have been a few studies on the application of soundproofing materials on medical equipment, which is the main cause of noise in a medical environment. [...] Read more.

Soundproofing materials are widely used in various fields as a passive measure to reduce noise. Despite this, there have been a few studies on the application of soundproofing materials on medical equipment, which is the main cause of noise in a medical environment. Despite the increasing number of studies on active noise control for the noise reduction of machines, it is difficult to apply customized noise control—i.e., specific control measures according to the various characteristics of that noise—due to its high cost and low effectiveness. Therefore, research on passive noise control using soundproofing materials is required for effective noise control. The 3D CAD/CAM milling machine, which is an essential device in the digitalized dental environment, is causing various problems as a new noise source. This study investigated the noise of the milling machine and considered its characteristics in application of an efficient soundproofing material for noise reduction. Additionally, a soundproofing material performance test was conducted to select an appropriate soundproofing material based on the noise characteristics of the milling machine. As milling machines cause noise issues in hospitals, the study results were analyzed in considering practical aspects for immediate application to actual sale products. This study suggests that the application of Thinsulator and a triple soundproofing mat (butyl 100% + aluminum + sound-insulating material) is effective in the noise reduction of milling machines. Full article

(This article belongs to the Special Issue Noise Barriers)

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20 pages, 4835 KiB

Open AccessArticle

On the Control of Low-Frequency Audible Noise from Electrical Substations: A Case Study

by Edoardo Alessio Piana and Nicolaas Bernardus Roozen

Appl. Sci. 2020, 10(2), 637; https://0-doi-org.brum.beds.ac.uk/10.3390/app10020637 - 16 Jan 2020

Cited by 9 | Viewed by 4307

Abstract

With the world facing the urgency of energy transition, the development of efficient and quiet electrical infrastructures is of topical importance in the construction of the environment of the future. The problem of noise from power distribution systems is often underestimated, although several [...] Read more.

With the world facing the urgency of energy transition, the development of efficient and quiet electrical infrastructures is of topical importance in the construction of the environment of the future. The problem of noise from power distribution systems is often underestimated, although several works in the literature underline the effect of disturbance on the population, especially concerning the low frequency range. This paper overviews the issue of the low-frequency noise generated by electrical substations, from the experimental characterization of the source to the possible mitigation measures at the source, along the propagation path and at the receiver. Alongside the general presentation, a case study serves as a practical demonstration of the proposed methodological approach. It was found that in the investigated situation the main disturbance comes from the transformer at two low-frequency harmonics of twice the networking frequency. A traditional noise barrier is designed taking into account the strict size constraints imposed by technical compatibility with the electrical infrastructure, which limits its efficacy at low frequency. Noise masking with broadband signals can be a complementary solution to further reduce noise disturbance and contain it within prescribed limits. The evaluation of subjective response of the receivers to different mitigation solutions is made possible by the availability of the impulse response. Full article

(This article belongs to the Special Issue Noise Barriers)

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13 pages, 1431 KiB

Open AccessArticle

Performance Evaluation of Active Noise Control for a Real Device Casing

by Krzysztof Mazur, Stanislaw Wrona and Marek Pawelczyk

Appl. Sci. 2020, 10(1), 377; https://0-doi-org.brum.beds.ac.uk/10.3390/app10010377 - 03 Jan 2020

Cited by 14 | Viewed by 2175

Abstract

Reduction of noise generated by devices is an important problem, both in industrial environments where high sound pressure levels may damage hearing, and in households where the sound pressure level is usually moderate, but may cause discomfort and stress. Classically used passive methods [...] Read more.

Reduction of noise generated by devices is an important problem, both in industrial environments where high sound pressure levels may damage hearing, and in households where the sound pressure level is usually moderate, but may cause discomfort and stress. Classically used passive methods often have poor performance for low frequencies. Alternatively, active control can be used to improve noise reduction in this frequency range. In the proposed approach, noise generated by devices may be reduced by controlling vibrations of the casing. The authors previously confirmed the performance of the proposed active control approach using a dedicated noise-canceling casing. Herein, we describe further development and application of the method to an off-the-shelf washing machine. Electrodynamic actuators were installed on four walls of the washing machine. The performance of the control systems was experimentally evaluated during the real spinning phase and the results are reported here. Full article

(This article belongs to the Special Issue Noise Barriers)

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Review

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27 pages, 2204 KiB

Open AccessReview

Comparative Study of Sound Transmission Losses of Sandwich Composite Double Panel Walls

by Chukwuemeke William Isaac, Marek Pawelczyk and Stanislaw Wrona

Appl. Sci. 2020, 10(4), 1543; https://0-doi-org.brum.beds.ac.uk/10.3390/app10041543 - 24 Feb 2020

Cited by 37 | Viewed by 8908

Abstract

The increasing motivation behind the recently wide industrial applications of sandwich and composite double panel structures stems from their ability to absorb sounds more effectively. Meticulous selection of the geometrical and material constituents of both the core and panels of these structures can [...] Read more.

The increasing motivation behind the recently wide industrial applications of sandwich and composite double panel structures stems from their ability to absorb sounds more effectively. Meticulous selection of the geometrical and material constituents of both the core and panels of these structures can produce highly desirable properties. A good understanding of their vibro-acoustic response and emission index such as the sound transmission loss (STL) is, therefore, a requisite to producing optimal design. In this study, an overview of recent advances in STL of sandwich and composites double panels is presented. At first, some salient explanation of the various frequency and controlled regions are given. It then critically examines a number of parameter effects on the STL of sandwich and composite structures. Literatures on the numerical, analytical and experimental solutions of STL are systematically presented. Efficient and more reliable optimization problems that maximize the STL and minimize the objective functions capable of degrading the effectiveness of the structure to absorb sounds are also provided. Full article

(This article belongs to the Special Issue Noise Barriers)

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