|Title:||Acoustical canyon effect in built environments|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Traffic noise -- China -- Hong Kong
|Department:||Department of Building Services Engineering|
|Pages:||viii, 101 leaves : ill. (some col.) ; 30 cm|
|Abstract:||Excessive low frequency traffic noise can affect everybody. It can lead to hearing loss and mental stress and irritation. It can also interfere with daily activities such as doing homework, watching television and talking on the telephone. The most important concentration of transportation noise was paid in the frequency above 500Hz and below 2000Hz, which is the dominant frequency of the heavy load traffic flow. In the present study, an investigation was conducted to evaluate the strength of the canyon along a traffic road. The attenuation capability of four different angles of facade to the line source and two special canyon arrangements were the target areas in the investigation. The main factors affecting the strength of city canyon were identified through the scale model measurements. It was found that the major factors for affecting the degree of canyon include multiple reflections and diffraction from the corner of the facade. Meanwhile, techniques of acoustic scale model measurement and analysis were developed. Based on these techniques, the reasons for contributing the strength of canyon effect along the traffic road were found. Resonance is another subject strongly affecting the strength of canyon effect along the traffic road. At the same time, one-third octave resonant frequencies were found to be related to the configuration of the canyon arrangement. A detailed study was conducted to find out the relationship between resonant frequency and the arrangements. Several tables of resonant frequencies were found and can be listed as reference to design the canyon arrangement. Extra reflection correction is added to the corner of the facades. This will contribute part of the sound level at the corner. The degree of reflection correction factor depends on all the reflecting facades on the opposite side of the road facing the reception point. With reference to the information obtained by several simulations, some suggestions to study the strength of canyon effect along traffic road are put forward. The future direction of similar discussion on canyon effect in different built environment is pointed out.|
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