Noise is unwanted sound, but determining what is "unwanted" can be highly subjective. What is music to one person may be a cacophony to another. The roar of nearby traffic may disturb and distract one individual, but barely be noticed by their neighbour. Tools have been developed over the years to measure noise levels and determine which levels are generally acceptable, but the results are often poorly understood

In Hong Kong, noise problems are exacerbated by crowded living conditions. Most people live in high-rise buildings, many of which are located next to busy roads and commercial and industrial areas. More than 10 000 complaints are made about excessive noise each year. The Environmental Protection Department (EPD) has introduced a number of measures to control noise, yet misunderstandings persist. One key point is that noise cannot be eliminated, only controlled. The department is therefore endeavouring to improve the public's understanding of noise and the many issues involved in reducing it to acceptable levels.

Education is needed to improve people's understanding of noise.

Noise can be measured in many different ways. The loudness, type of sound, duration, time of day it occurs, and distance from the noise receiver can all determine whether it is regarded as an unwanted intrusion. These factors also complicate how noise can be measured and mitigated against. The EPD has developed a tool that will help people understand noise in all its complexities and learn how to prevent noise.

A noise education seminar to promote public's understanding of noise.

A noise education website was launched in 2003, after being refined to make it more user-friendly. Visitors can listen to different noise types, learn how noise levels are calculated and understand different control and mitigation measures, through interactive panels, text and illustrations (http://www.epd.gov.hk/epd/noise_education). The general public can use the website to find out about common noise sources and what can be done about unwanted noise. A version for young people is also featured, which explains noise in simpler terms.

One area that is often controversial is the definition of "acceptable" noise. The EPD uses the noise standard 70 decibel L₁₀ (1 hour) to measure traffic noise, which indicates that noise has exceeded 70 decibel one-tenth of the time (six minutes per hour) during which the measurement was taken. This is regarded as a fair measure of traffic noise nuisance. But how did that measurement become the standard? The website explains that extensive research in England in the 1960s found the L₁₀ measurment correlated well with the community's tolerance and complaints about traffic noise. The standard was formulated in the late 80s after extensive field measurements in Hong Kong and a review of similar standards in other developed countries. The website provides many insights like these in order to illustrate that the noise standards in Hong Kong have been well-researched and are not randomly determined.

Much of the information on the website also has uses for professionals, such as engineers, for whom noise may be a by-product of their work. They can refresh their knowledge on the basic scientific principles for analysing noise and look up real examples of mitigation and control measures that have been used in Hong Kong. The website also provides links to other sources of technical information.

People can learn about noise, its control and mitigation measures from the EPD's noise education website.

Going on-line to educate people about noise - and doing it in laymen's language, rather than the technical jargon used by practitioners - is part of the EPD's efforts to promote community understanding about environmental noise. This was an objective in the Chief Executive's 2001 policy address and the department is using other tools, in addition to the website, to meet this goal. A CD-ROM on environmental noise has been produced with input from more than 100 teachers, and includes interactive features and information about various noise sources. It will be distributed to schools, public libraries, district offices and professional institutes in 2004. Education initiatives are also being introduced for noise producers, such as the construction industry, to help them address the problem.

Construction noise has been a persistent source of complaint. In order to build new buildings, tear down old ones or renovate existing premises, it is inevitable that some noise is produced. The EPD has introduced a number of measures over the years to restrict the times when noisy work is allowed and to require that quieter equipment be used where possible. Nonetheless, construction work is still a source of unwelcome sound intrusion. The EPD must try to strike a balance between meeting demand for a quieter environment, and not unduly interfering with economic development.

In order to encourage operators to reduce their noise and obey the law, the EPD has formed partnerships with the construction industry, vehicle repair workshops, restaurants and property managers in recent years. The four industries receive advice and support in controlling noise, while the EPD gains a better understanding of the constraints and opportunities they face. The partnership programme is helping to reduce complaints and violations as these industries learn more about how to control their noise (see Customer Service and Partnership chapter for more details). In addition, education efforts are being targeted at specific operators. The EPD and Highways Department began staff exchanges in October 2003 to better understand each other's work and it is hoped this will lead to a better appreciation of road-related noise problems.

(Left) Information on designated noise control areas and noise permits can be accessed through the Internet. (Middle) EPD works with the industry for a quieter environment. (Right) Our partnership with the construction industry improves communication with the trade on the legal requirements of noise control and mitigation measures for noisy construction work.

The Internet is also being used to smooth the way for operators to deal with noise on a day-to-day basis. Operators can check instantly whether their work will be carried out in an area designated for noise control, through the EPD website (http://www.epd.gov.hk/epd/english/environmentinhk/noise/noise_maincontent.html). They can also check to see if other noise permits have been issued in the area, as all noise permits are now being published on the website. Operators can use information about noise permits issued for nearby construction sites when planning permit applications, and adjust their work schedules to minimise disruptions. Self-assessment tools are available on-line so builders can evaluate the likely noise impact from their construction sites. Builders can also submit their noise permit applications electronically.

The publication of noise permits also helps the public to develop a better understanding of noise control. People can visit the website to determine if a site has a permit, how long the work will last and what conditions have been attached to it, such as the times of day that noisy work is allowed. One of the most annoying factors with noise is not knowing when it will end. The noise permit information plugs that gap and also indicates whether an operator is working outside their permitted terms.

		Noise from domestic renovation work can be very annoying, so the EPD has drafted guidelines on renovation work to minimise potential problems. The guidelines are targeted at property managers and provide advice on controlling noise. For example, property managers should make residents aware of the statutory requirements through posters and other publications, and alert them to their rights and obligations under the Deed of Mutual Covenant. Property managers should also exercise their right to impose conditions and inspect premises to reduce noise, as specified in the Deed of Mutual Covenant, Building Management Ordinance and house rules. And they are advised to help Owners Corporations draft house rules on such things as the permitted hours for noisy work and the need to have a renovation permit. The guidelines have been distributed to property management companies and can also be viewed on the EPD website at http://www.epd.gov.hk/epd/english/environmentinhk/noise/guide_ref/files/laco.pdf Meanwhile, the EPD has also formulated a Code of Practice for the construction trade in regard to a 2002 amendment to the Noise Control Ordinance that holds company directors liable for noise offences. The Code of Practice provides guidelines on good management practice in managing noise and preventing violations. It was drafted in consultation with the affected industries and supported by the Legislative Council's Environmental Affairs Panel. Following the finalisation of the Code, the amendment will be put into operation in 2004. Noise emanates from building renovation activity.

Noise education is a two-way process. While the EPD can inform people about noise standards and prevention, it is also working on gaining a better understanding of the issue. Given the high-density living of Hong Kong and the wide variety of noise sources, there is much to learn about noise pollution here. Musical noise at home.		Noise in a crowded place. In 2003 a study was commissioned to obtain typical noise levels in different parts of Hong Kong. The focus is on noise experienced by people in daily life, in such places as the home, restaurants, karaoke bars, game centres, concert halls, beaches, barbecue sites, urban parks and country parks. Noise levels in the home will be measured
at different times of the day, while at other sites they will be measured during the likely peak noise hours. The study will also appraise the effectiveness of measures that have been introduced to reduce traffic noise, such as podiums, purpose-built balconies, architectural fins, barriers and low-noise road surfaces (see box for details). The study will take about two years to complete and it is hoped that it will provide information for formulating new policies and measures to control noise.

		Embankment Road in Mong Kok is one of the roads on trial with low-noise surfaces.     Traffic noise can be effectively screened off by barriers.   More than one million people in Hong Kong are affected by excessive traffic noise. The EPD has introduced programmes to minimise noise from new roads and address the problem of existing roads. Noise from new roads can be managed through planning and the building of enclosures where necessary. But for existing roads, the solutions are more difficult. The three main options - barriers, low-noise road surfaces and traffic management measures - all have constraints. More than 30 roads have been identified as suitable for retrofitting noise barriers. The first batch to be retrofitted involves three roads where thousands of residents in housing estates are exposed to excessive road noise. However, not all residents support the barriers and some prefer that a low-noise surface be tried out first. The Government has agreed to do so on Yuen Shin Road, with the provision that a noise barrier could be erected later if necessary. Low-noise surfaces can reduce noise by a few decibels but are not suitable for every road. They are especially not effective on roads with steep inclines, sharp bends and heavy use by commercial vehicles. Nonetheless, 72 roads have been identified for a trial of low-noise surfaces and work began in 2003. More than 550 roads are not suitable for either barriers or low-noise surfaces. Noise may be reduced through traffic management measures, such as diverting traffic, if they are feasible and practicable. However, a proposal to introduce such measures was objected to strongly by the transport trade in 2003.

Noise is annoying but it is something that everyone in an urban environment must learn to live with. The goal is to make it as acceptable as possible to the majority of residents. This can be a difficult balance to achieve, but the EPD hopes that by educating people and undertaking programmes to reduce noise, it is moving towards making Hong Kong a quieter city.

		Noise barriers are a fact of life in most cities around the world, where road, rail and air transport all increase noise levels. Blocking out noise by barriers and enclosures is effective in reducing the noise nuisance, and Hong Kong has built 38 kilometres of noise barriers and enclosures. But these have come under criticism in recent years for their visual impact. The EPD jointly organised an international seminar in December 2003 to look at the effectiveness and aesthetics of noise barriers. Provision of noise control and mitigation measures are now featured in new railway projects. More than 160 professionals attended the event, which was jointly sponsored by the EPD, Highways Department, Hong Kong Polytechnic University and Hong Kong Institute of Acoustics. Speakers came from Australia, Belgium, Britain and Japan, as well as Hong Kong. They discussed such issues as theories of barrier design, methods for assessing their performance, and new technologies. One subject that sparked great interest was the visual impact of barrier design. It was pointed out that many issues need to be resolved, such as whether a barrier should stand out or blend into the background, what attention should be paid to residents' view of the barrier, and how to reconcile cost with demands for more attractive barriers. The keynote speakers also noted that avoiding noise problems through planning was the best solution.