Performance of profiled single noise barriers covered with quadratic residue diffusers

Monazzam, Mohammad Reza; Lam, Y. W.

doi:10.1016/j.apacoust.2004.08.008

Cited by 64 publications

(47 citation statements)

References 13 publications

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“…Barrier caps, in theory, allow improving barriers already put in place (retrofitting). Complex shapes have been studied and optimized before [20][21][22][23][24][25]. To study the improvement in performance by adding absorbing caps, three basic shapes were numerically evaluated with a 2D-BEM technique in Ref.…”

Section: Noise Walls With Vegetated Capsmentioning

confidence: 99%

Using natural means to reduce surface transport noise during propagation outdoors

et al. 2015

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a b s t r a c tThis paper reviews ways of reducing surface transport noise by natural means. The noise abatement solutions of interest can be easily (visually) incorporated in the landscape or help with greening the (sub)urban environment. They include vegetated surfaces (applied to faces or tops of noise walls and on buildings' façades and roofs), caged piles of stones (gabions), vegetation belts (tree belts, shrub zones and hedges), earth berms and various ways of exploiting ground-surface-related effects. The ideas presented in this overview have been tested in the laboratory and/or numerically evaluated in order to assess or enhance the noise abatement they could provide. Some in-situ experiments are discussed as well. When well designed, such natural devices have the potential to abate surface transport noise, possibly by complementing and sometimes improving common (non-natural) noise reducing devices or measures. Their applicability strongly depends on the available space reserved for the noise abatement and the receiver position.

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Section: Noise Walls With Vegetated Capsmentioning

confidence: 99%

Using natural means to reduce surface transport noise during propagation outdoors

et al. 2015

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“…This was already explained for quadratic residue diffuser edge barrier by Monazzam and Lam (2005). It seems that the diffuser surface redirects some of the sound wave upward, hence the low performance of the diffusive barrier is expected at these zones.…”

Section: Sequence Effectmentioning

confidence: 94%

“…Fujiwara et al (1998) has shown that a uniform series of rigid wells in the upper surface of a T-shape barrier produces insertion loss values equal to those of a soft surface over a significant range of frequencies. In respect to the use of Quadratic Residue Diffuser (QRD) to cover the top of the barrier, Monazzam and Lam (2005) has shown that a T-shape barrier design produces a higher barrier A-weighted insertion loss than using a typical fibrous absorbent material on the barrier. A similar type of examination for T-shape barriers is shown in Baulac et al (2008).…”

Section: Introductionmentioning

confidence: 99%

Performance of Environmental T-shape Noise Barriers Covered with Primitive Root Diffusers

Monazzam¹,

Naderzadeh²,

Nassiri³

et al. 2010

Archives of Acoustics

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There is a considerable increase in the use of noise barriers in recent years. Noise barriers as a control noise solution can increase the insertion loss to protect receivers. This paper presents the results of an investigation about the acoustic efficiency of primitive root sequence diffuser (PRD) on an environmental single T-shape barrier design. A 2D boundary element method (BEM) is used to predict the insertion loss of the tested barriers. The results of rigid and with a different sequence diffuser coverage are also predicted for comparison. Employing PRD on the top surface of T-shape barrier has been found to improve the performance of barriers in comparison with the use of rigid and QRD coverage at the examined receiver locations. It has been found that decreasing the design frequency of PRD shifts the frequency effects towards lower frequencies, and therefore the overall A-weighted insertion loss is improved. It was also found that using wire mesh with reasonably efficient resistivity on the top surface of PRD improves the efficiency of the reactive barriers; however utilizing wire meshes with flow resistivity higher than the specific acoustic impedance of air on the PRD top of a diffuser barrier significantly reduces the performance of the barrier within the frequency bandwidth of the diffuser. The performance of a PRD covered T-shape barrier at 200 Hz was found to be higher than that of its equivalent QRD barriers in both the far field and in areas close to the ground. The amount of improvement compared made by PRD barrier compared with its equivalent rigid barrier at far field is about 2 to 3 dB, while this improvement relative to the barrier model "QR4" can reach up to 4-6 dB.

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“…For simplicity, an equivalent frequency of 550 Hz can be set to represent the total frequency band in the calculation of diffraction suggested in the FHWA traffic noise model [27]. In the 1/3rd-octave-band spectrum, the frequency of 500 Hz is used in the approximate calculation of diffraction and noise reduction effect of a sound barrier [9,[28][29][30][31]. However, the data used was collected from 1993 and 1995, and the characteristics of vehicle noise have changed since then because of the variety of vehicle types and speeds [32].…”

Section: Introductionmentioning

confidence: 99%

“…Current research on noise barriers primarily focuses on noise calculation [8,9], the effects of barrier shapes [10,11], and the design of barriers [12][13][14][15]. As one of the important aspects, prediction of the insertion loss by the noise barrier has been attracting the attention of scholars, and both mathematical and experimental approaches have been developed.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Noise Barrier Insertion Loss Based on Varied Vehicle Frequencies

Wang

Luo²,

Cai

2018

Applied Sciences

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A single frequency of 500 Hz is used as the equivalent frequency for traffic noise to calculate the approximate diffraction in current road barrier designs. However, the noise frequency changes according to the different types of vehicles moving at various speeds. The primary objective of this study is the development of a method of calculating the insertion loss based on frequencies. First, the noise emissions of a large number of vehicles classified by speed and type were measured to obtain data the noise spectrum. The corresponding relation between vehicle type, speed, and noise frequency was obtained. Next, the impact of different frequencies on the insertion loss was analyzed and was verified to be reasonable in experiments with different propagation distances compared to the analysis of a pure 500 Hz sound. In addition, calculations were applied in a case with different traffic flows, and the effect of a road noise barrier with different types of constituents and flow speeds were analyzed. The results show that sound pressure levels behind a barrier of a heavy vehicle flow or with a high speed are notably elevated.

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Performance of profiled single noise barriers covered with quadratic residue diffusers

Abstract: Abstract

Cited by 64 publications

References 13 publications

Using natural means to reduce surface transport noise during propagation outdoors

Using natural means to reduce surface transport noise during propagation outdoors

Performance of Environmental T-shape Noise Barriers Covered with Primitive Root Diffusers

Calculation of Noise Barrier Insertion Loss Based on Varied Vehicle Frequencies

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