Volume 6, Number 1 (spring 2009)                   ioh 2009, 6(1): 44-55 | Back to browse issues page

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Monazam M, Nasiri P, Javid Rouzi N. Contribution of diffuser surfaces to efficiency of tilted T shape parallel highway noise barriers. ioh. 2009; 6 (1) :44-55
URL: http://ioh.iums.ac.ir/article-1-162-en.html

, mmonazzam@hotmail.com
Abstract:   (6019 Views)

Background and aims

The paper presents the results of an investigation on the acoustic  performance of tilted profile parallel barriers with quadratic residue diffuser tops and faces.


A2D boundary element method (BEM) is used to predict the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface and faces of all tilted profile parallel barrier models introduced here is found to  improve the efficiency of barriers compared with rigid equivalent parallel barrier at the examined  receiver positions.


Applying a QRD with frequency design of 400 Hz on 5 degrees tilted parallel barrier  improves the overall performance of its equivalent rigid barrier by 1.8 dB(A). Increase the treated surfaces with reactive elements shifts the effective performance toward lower frequencies. It is  found that by tilting the barriers from 0 to 10 degrees in parallel set up, the degradation effects in  parallel barriers is reduced but the absorption effect of fibrous materials and also diffusivity of the

quadratic residue diffuser is reduced significantly. In this case all the designed barriers have better  performance with 10 degrees tilting in parallel set up.


The most economic traffic noise parallel barrier, which produces significantly  high performance, is achieved by covering the top surface of the barrier closed to the receiver by  just a QRD with frequency design of 400 Hz and tilting angle of 10 degrees. The average Aweighted  insertion loss in this barrier is predicted to be 16.3 dB (A).

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Type of Study: Research | Subject: Assessment and risk management
Received: 2009/10/3

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