Feasibility study of green noise barriers in Hong Kong

Abstract

Hong Kong is a crowded city where pavements, lanes, hawker areas, trunk roads and highway are closely built. With heavy traffic flow on complex road networks, the noise barriers located in the urban centre usually adjacent to commercial centres and residential buildings. The design of noise barriers is therefore needed to be in harmony with the landscape of the neighbourhood. Different kinds of green noise barrier systems combined with soil and vegetation had been developed across Europe and the USA in recent years. It is believed that an effective controller of noise shall be visually attractive especially for residents who are adjacent to the roads. A number of noise barriers with vegetation were successfully implemented in European Countries. Nevertheless, these engineering techniques cannot be fully applied to Hong Kong due to the over-crowded living environment.

A well-designed green noise barrier system is the critical reason for successful application to sustain the vegetation and to insulate and absorb noise. The objective of this study to investigate different kinds of green noise barriers and come up with some guidelines for design consideration in order to optimize the green noise barriers. The study provides a thorough analysis of the available green noise barrier systems across the world, including a look at all the potentials benefits from environmental and socio-economics perspectives.

The pilot field measurement was conducted at Yeung Uk Road where green noise barriers located between a heavily travelled main road and residential area in Tsuen Wan, to measure the SPL and Leq noise levels to assess the effectiveness of the green noise barriers. No significant attenuation effect is observed on the green noise barrier which has to be attributed to the median placement and over-crowded urban environment.

Online questionnaires and interviews are conducted to investigate the effects of vegetation on the perception of green noise barriers. Results show that 78% of the respondents preferred vegetation rather than concrete (0.1%) and other materials. 77% like the aesthetics appearance of vegetation and 86% are willing to bear the cost. In general, 95% of the respondents agreed green noise barriers should be promoted in Hong Kong. The results assured that (1) vegetation on green noise barrier is aesthetically pleasing and mostly preferred; (2) people are willing to pay for green noise barrier for aesthetics; (3) aesthetic or vegetated screen is important in determining human response to noise which improved public perception of traffic noise due to visual and psychological relief.

The outcome of the study indicated that it is feasible to promote green noise barriers in Hong Kong, with the evidence of the potential benefits, technical experience and public support. It is also suggested that the living wall modular system is the best system which is suitable for the application in Hong Kong.