Three dimensional quasi-periodic noise barriers (original) (raw)
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Three-dimensional analysis of a noise barrier using a quasi-periodic boundary element method
The Journal of the Acoustical Society of America, 2015
Two-dimensional (2D) numerical models are often used to estimate the environmental noise attenuation of a roadside barrier. The prediction of noise barrier attenuation using a 2D boundary element model assumes an infinitely long barrier with constant cross section. However, for barrier geometries that do not have constant cross section in the third dimension, three-dimensional (3D) models should be used for greater accuracy of noise reduction due to the barrier. The size of a numerical model and hence its computational cost can be significantly reduced using a 3D quasi-periodic structure, whereby the structure is truncated using a finite number of periodic sections. In this study, a quasi-periodic model developed using the boundary element method is used to predict the acoustic performance of 3D noise barriers. The convergence behavior of the quasi-periodic model is discussed. Results from the quasi-periodic model are compared with results from both a 3D analytical model and a 2D fi...
Performance Analysis of a 3D Rigid Noise barrier in an Acoustic Medium
Performance analysis of a single vertical rigid barrier in an acoustic medium, as a part of rigid noise barriers (parallel barriers), is accomplished. First the governing equation of acoustic medium which contains an inviscid fluid is used to analyze the performance of the barrier which is under the radiation of a monopole acoustic source. Acoustic medium has been surrounded with some very tall and rigid walls. The acoustic pressure in the medium is considered as a superposition of incident and scattered wave. The governing equation of acoustic media in conjunction with the boundary conditions due to existence of the barrier and rigid walls are solved simultaneously using a numerical technique namely generalized differential quadrature method (GDQ). The effects of the source and walls locations, dimensions of the barrier and the excitation frequency on the total acoustical pressure and also the insertion loss factors around the barrier are studied.
Recent Developments of Noise Attenuation Using Acoustic Barriers for a Specific Edge Geometry
Computation
The aim of this research is to provide a better prediction for noise attenuation using thin rigid barriers. In particular, the paper presents an analysis on four methods of computing the noise attenuation using acoustic barriers: Maekawa-Tatge formulation, Kurze and Anderson algorithm, Menounou formulation, and the general prediction method (GPM-ISO 9613). Accordingly, to improve the GPM, the prediction computation of noise attenuation was optimized for an acoustic barrier by considering new effects, such as attenuation due to geometrical divergence, ground absorption-reflections, and atmospheric absorption. The new method, modified GPM (MGPM), was tested for the optimization of an y-shape edge geometry of the noise barrier and a closed agreement with the experimental data was found in the published literature. The specific y-shape edge geometry of the noise barrier contributes to the attenuation due to the diffraction phenomena. This aspect is based on the Kirchhoff diffraction the...
A methodology for optimum design of Y-shape noise barriers
A method for designing optimum shape Y-noise barriers is performed using a 2D-boundary element method modelling and evolutionary computation. The model assumes an infinite, coherent line source of sound, parallel to an infinite noise barrier of uniform cross section and surface covering along its length, where a maximum limit to the effective height of the barrier designs is imposed. The study is carried out in frequency domain. The proposed fitness function to minimize is the sum of squared differences corresponding to the insertion loss (IL) throughout a set of frequencies belonging to the one-third octave band spectra (fourteen values are taken into account) of two barriers: the candidate Y-barrier design and a reference noise barrier design (a simple barrier with higher effective height than the maximum constrained value of the design). Shape optimization is accomplished by forcing the design to fit a IL reference curve corresponding to a higher effective height simple barrier and to obtain a Y-shape design whose IL curve performance fits this reference. The obtained results succeed in accomplishing the imposed requirements. Results are detailed in terms of IL values and barrier shape designs, numerically and graphically.
Acta Acustica United With Acustica, 2017
Barriers are widely used to attenuate environmental noise from vehicles to residential areas. This paper numerically explores the acoustic performance of ab arrier for tailored lowf requencyn oise reduction using aq uasiperiodic boundary element method, whereby the barrier is represented by afi nite number of periodic sections along its length. Results for the insertion loss of ab arrier with single and multiple Helmholtz resonators embedded along the top edge of each periodic barrier section and tuned to different frequencies are compared to results for an equivalent straight barrier in the absence of the Helmholtz resonators. The acoustic performance of the noise barrier with and without the embedded Helmholtz resonators is also examined for elevated trafficnoise sources typically corresponding to engine and exhaust noise of light and heavy vehicles. Diffraction overthe top edge of the barrier and reflections from the ground on both the source and receiversides of the barrier are taken into account.
Evaluating the Effectiveness of Novel Noise Barrier Designs
2000
In recent years there has been growing interest in the use of noise barrier profiles that can enhance the diffraction efficiency of plane barriers. These are placed on the top of the barrier in order to reduce sound diffracted into the shadow zone. Despite numerous demonstrations that the profiles enhance performance there is as yet no universal agreement on how
Urban Science
Noise barriers are a critical part of noise mitigation in urban and rural areas. In this study, a comparison of the insertion loss calculations of noise barriers via the Finite Element Method (FEM) and various formulae (Kurze–Anderson, ISO 9613-2/Tatge, Menounou) is presented in the case of two-dimensional acoustic radiation problems. Some of the cases explored include: receiver in the illuminated zone, in the shadow zone, in the shadow border, source in medium, long, short distance from the barrier, source and receiver near barrier, and source above the barrier. Comparisons of the results indicate that FEM results comply well (less than 1 dB in each case) with Menounou’s formula which in turn complies with the analytic solution (MacDonald Solution). In certain cases, the differences between FEM and Menounou’s formula compared to Kurze–Anderson and ISO 9613-2/Tatge formulae are substantial (source and receiver near the barrier (10 dB) and source near the barrier and receiver in the ...
Efficient Calculation of the Three-Dimensional Sound Pressure Field Around a Noise Barrier
Journal of Sound and Vibration, 1996
A numerical method is presented for calculating the sound pressure around a noise barrier of constant but arbitrary cross-section. To obtain the exact solution of this problem, the Helmholtz equation must be solved in the three-dimensional domain outside the barrier. It is shown in this article how to calculate this 3-D sound pressure from solutions of simpler problems defined on the two-dimensional domain outside a cross-section of the barrier. The numerical solution of a large three-dimensional problem is thus avoided and the efficiency of the calculation is considerably improved especially when a whole frequency spectrum is needed. By using the boundary element method to calculate the numerical solutions in the two-dimensional domains, examples are given of determinations of sound pressure fields created by a point source and by an incoherent line source. In this way the efficiency of barriers of different cross-sections can be compared by using the real sound pressure around them. From the frequency spectrum at a point, one can then calculate by Fourier transform the temporal variations of the sound pressure created by a noise source moving in a direction parallel to the barrier.