Design of absorptive parallel barriers

Pao Yue-kong Library Electronic Theses Database

Design of absorptive parallel barriers

 

Author: Mak, Wai-kwong
Title: Design of absorptive parallel barriers
Degree: M.Sc.
Year: 2000
Subject: Noise barriers -- China -- Hong Kong
Noise barriers -- China -- Hong Kong -- Design and construction -- Data processing
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Civil and Structural Engineering
Pages: xiii, 140, [26] leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1504109
URI: http://theses.lib.polyu.edu.hk/handle/200/3000
Abstract: Noise barriers have been widely used to protect noise sensitive receivers. However, urban townscape in Hong Kong is dominated by high-rise buildings, which were built close to the roadway. Parallel barrier and high-rise buildings are acting as reflective surfaces to degrade the acoustic performance of noise barrier. The use of conventional barrier design simply locating the receivers within the shadow zone is not sufficient in the above situation. This study employed computer model as a simple and effective means suitable for barrier design. The computer model was based on the mathematical theories given by 'Calculation of Road Traffic Noise' (CRTN) to predict the sound level at the noise sensitive receivers and image source theory was also incorporated particularly to evaluate the reflection effect. Site measurements were carried out at three locations with barrier built in Hong Kong and the computer program was used to predict the noise level for comparison. Comparing the results with the environmental impact assessment reports by consultants had revealed that the reflection effect of opposite facades was not considered and the use of barrier type was not mentioned. The predicted noise levels based on consultant's estimate on the future traffic flow found that the case study of the Lung Cheung Road and Tai Po Road (Ho Tung Lau) would be exceeded the noise limit L10 70 dB(A). The absorptive parallel barriers, tilted barrier and central barrier were proposed as mitigation measures to eliminate the significant reflection effect. Site investigations on existing barriers found that the provision of parallel barriers and central barriers in Hong Kong was not carefully considered and planned. Study on measured noise spectrum of heavy vehicles indicated that the dominant noise was at low frequency about 50Hz ~ 200Hz. If the absorptive barrier's materials were appropriately selected in terms of both durability and acoustic performance, the absorptive parallel barriers would be an economic and effective substitution for partial enclosure.

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