scholarly journals Numerical Evaluation of Sound Attenuation Provided by Periodic Structures

2013 ◽  
Vol 38 (4) ◽  
pp. 503-516 ◽  
Author(s):  
Mário Martins ◽  
Luís Godinho ◽  
Luís Picado-Santos
Keyword(s):  
Periodic Structures ◽  
Traffic Noise ◽  
Fundamental Solutions ◽  
Sound Attenuation ◽  
Method Of Fundamental Solutions ◽  
Noise Sources ◽  
Noise Abatement ◽  
Acoustic Performance ◽  
Sonic Crystals ◽  
Different Sources

Abstract The use of periodic structures as noise abatement devices has already been the object of considerable research seeking to understand its efficiency and see to what extent they can provide a functional solu- tion in mitigating noise from different sources. The specific case of sonic crystals consisting of different materials has received special attention in studying the influence of different variables on its acoustic performance. The present work seeks to contribute to a better understanding of the behavior of these structures by implementing an approach based on the numerical method of fundamental solutions (MFS) to model the acoustic behavior of two-dimensional sonic crystals. The MFS formulation proposed here is used to evaluate the performance of crystals composed of circular elements, studying the effect of varying dimen- sions and spacing of the crystal elements as well as their acoustic absorption in the sound attenuation provided by the global structure, in what concerns typical traffic noise sources, and establishing some broad indications for the use of those structures.

scholarly journals Solving Noise Pollution Issue Using Plenum Window with Perforated Thin Box

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 614
Author(s):  
Hsiao Mun Lee ◽  
Andi Haris ◽  
Kian Meng Lim ◽  
Jinlong Xie ◽  
Heow Pueh Lee
Keyword(s):  
White Noise ◽  
Traffic Noise ◽  
Noise Pollution ◽  
Experimental Results ◽  
Frequency Range ◽  
Noise Mitigation ◽  
Noise Sources ◽  
Acoustic Performance ◽  
Common Noise ◽  
The Common

In the present study, a conventional plenum window was incorporated with perforated thin box in order to enhance its performance at frequency range which centralized at 1000 Hz as most of the common noise sources at city nowadays are centralizing around this frequency. The entire studies were conducted in a reverberation room. The effectiveness of jagged flap on mitigating diffracted sound was also studied. Three types of noises were examined in the current study—white noise, traffic noise and construction noises. The experimental results showed that the plenum window with perforated thin box could reduce 8.4 dBA, 8.7 dBA and 6.9 dBA of white, traffic and construction noises, respectively. The jagged flaps did not have significant effect on the plenum window’s noise mitigation performance. When frequencies were ranging from 800 Hz to 1250 Hz, when compared with the case of without perforated thin box, it was found that the perforated thin box had good acoustic performance where it was able to reduce additional 1.6 dBA, 1.6 dBA and 1.2 dBA of white, construction and traffic noises, respectively.

Parametric Study on Rectangular Sonic Crystal

2012 ◽  
Vol 152-154 ◽  
pp. 281-286 ◽  
Author(s):  
Arpan Gupta ◽  
Kian Meng Lim ◽  
Chye Heng Chew
Keyword(s):  
Band Gap ◽  
Periodic Structure ◽  
Parametric Study ◽  
Sound Propagation ◽  
Periodic Structures ◽  
Sound Attenuation ◽  
Experimental Results ◽  
Center Frequency ◽  
Sonic Crystal ◽  
Sonic Crystals

Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

An Efficient MFS Formulation for the Analysis of Acoustic Scattering by Periodic Structures

2018 ◽  
Vol 26 (01) ◽  
pp. 1850003 ◽  
Author(s):  
L. Godinho ◽  
P. Amado-Mendes ◽  
A. Pereira ◽  
D. Soares
Keyword(s):  
Periodic Structures ◽  
Acoustic Scattering ◽  
Numerical Approach ◽  
Fundamental Solutions ◽  
Point Of View ◽  
Method Of Fundamental Solutions ◽  
Memory Usage ◽  
Computational Point ◽  
Efficient Memory ◽  
Element Method

The acoustic behavior of periodic structures has been a subject of intense study in recent years. From the computational point of view, these devices have mostly been analyzed using strategies such as the multiple scattering theory (MST) or numerical methods such as the finite element method (FEM). Some recent works propose the use of boundary methods, such as the method of fundamental solutions (MFS) or the boundary element method (BEM). However, the geometry and the large number of scatterers of these devices can lead to very large memory requirements and CPU times, which, particularly in the case of 3D problems, can be prohibitive. Here, a new numerical approach based on a frequency domain MFS formulation is proposed for 3D problems, allowing the analysis of very large problems. In this approach, the periodic character of the devices is used to define a matrix with a block structure, in which repeated blocks are only calculated once. In addition, an adaptive-cross-approximation (ACA) approach is incorporated to allow a more efficient memory usage, reducing the global computational requirements, and allowing the analysis of devices with hundreds of scatterers with a minimal memory usage.

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