Monitoring Environmental Noise Pollution

Evaluating the significance of noise and the effectiveness of current standards and legislations

Noise pollution is a problem controlled and managed by numerous pieces of legislation, standards and documents providing guidance. In the UK, each piece of guidance or legislation varies sufficiently to cause a certain degree of conflict, which can lead to confusion and conflict amongst site operators, developers, regulators and the general public.

Reasons for measuring noise

The most typical reason for measuring noise pollution is in response to a specific nuisance issue, perhaps relating to an industrial process or restaurant near a residential area.

The second reason for completing noise monitoring is to provide data to support planning applications where a potential nuisance or loss of amenity is anticipated which may lead to planning refusal or the imposition of control conditions.

Within the UK and Europe, some staggering statistics exist for people affected by various forms of noise:

• 450 million people are exposed to environmental noise >55dBA causing annoyance and disturbance of sleep
• 63% of the UK population are exposed to night-time levels exceeding 45 dB LAeq [guideline value] recommended by WHO
• 7% of dwellings that faced main roads were exposed to noise above 68 dB L10,18hr which is the qualifying level for sound insulation works under Noise Insulation Regulations for new roads
• 113 million people are exposed to environmental noise >65dBA which has serious consequences for health
• 10 million people are exposed to environmental noise >75dBA which is unacceptable for human habitation and can lead to hearing loss
• 30 million people are exposed to occupational noise >75dBA which is hazardous to hearing

Types and sources of noise and likelihood of nuisance

Clearly, the louder the noise source the greater the risk of disturbance and complaint. However, the character of the noise is also crucial. For instance, a tonal sound such as a hum or an intermittent noise will be more disturbing than a noise consisting of a varied range of frequencies.

How disturbing a noise will also depend on the level of ‘masking noise’ or background noise there is. In the UK, one specific industrial noise standard rates industrial noise by how much it exceeds background noise, the greater the difference the higher the likelihood of a nuisance complaint.

In addition to the logical and measurable, human perception of noise must also be considered in the way it is measured, assessed and controlled. One key issue is how ‘reasonable’ a noise is. For instance, the use of a power drill for a few hours during daylight hours is less disturbing than the same activity in the evening with the windows open, simply because one will be regarded as reasonable while the other is certainly not. However, there are inherently disturbing noises that obviously need control at all times, such as gun shots, dog barks and the problem of the repetitive low frequency beat of modern music.

Therefore it is impossible to set simplified, generic targets for the control of noise which provides much scope for arguments and debates, which can unfortunately lead to a finale in a judicial setting. An acoustic consultant should, however, hold the appropriate range of experiences, skills, tools and equipment to be able to assess any issue, guided by the various standards and legislation. Critically, they should also to be in the position to disagree, modify, or use their experience to interpret the standards if they feel that the situation requires them to do so.

Sources of environmental noise are numerous but can be simplified into four main categories, those being industrial noise, construction noise, traffic noise and leisure noise.

Industrial noise

In the UK, BS 4142:1997 “Rating Industrial Noise Affecting Mixed Residential and Industrial Areas” is the most important guidance document when considering industrial noise. This particular standard is most frequently used by regulatory bodies to determine the degree of noise nuisance from an industrial source.

In simple terms, the perceived source of nuisance is measured or predicted and adjusted for disturbing noise features such as ‘tones’ and ‘intermittency’, two key issues in assessing the impact of a noise. The adjusted level is compared with background noise (typically during night time measurement), residual noise (noise arising from sources other than the specific noise under investigation).

A difference of +10dB is a positive indication that complaints are likely, a difference of -10dB is a positive indication that complaints are unlikely and a difference of +5dB is considered to be of marginal significance.

BS 4142:1997 is the main tool used for planning assessments where industrial noise is or is expected to be the main issue in any planned development, whether new housing near existing industrial operations or a new factory near to existing housing. Planners, typically under advice from regulators, may impose boundary noise limits or planning consent levels. These conditions are often rigidly imposed but are typically very vague, which can cause ongoing complaints. There is no alternative to completing a properly conducted nuisance assessment.

Planning consent levels have to be relevant, bespoke and must clearly serve a positive purpose rather than arbitrarily place controls. Rigid and ill-composed consent levels will generate a consistent stream of appeals if a source of industrial noise is quiet enough not to disturb neighbours but is so close to the boundary that it exceeds an ill considered consent level. Conversely, many site operators believe that religiously complying with a set consent level will ensure they are immune from any legal action, when in reality the situation is far more complex.

Specific controls relating to construction sites

Although noise issues relating to construction noise are likely to be short term (possibly acute) rather than long term, the UK has separate Guidance (BS5228) for construction sites. In particular, Part 1:1984, “Code of practice for basic information and procedures for noise control” is a useful document because as well as giving general advice it describes a method for predicting noise from construction sites. BS5228 Part 1 does not specify suitable daytime noise levels from construction sites, but lists a number of factors which might affect the acceptability of noise and vibration from construction sites. These factors are:

• Site location
• Existing ambient noise levels
• Duration of site operations
• Hours of work
• Attitude to site operator
• Noise and vibration characteristics of the work

Where construction work must continue into the evening BS 5228 suggests that acceptable noise levels in the evening may need to be 10 dB(A) lower than daytime levels.

BS 5228 suggests that noise levels at the facades of occupied dwellings may need to be as low as 40dB (LAeq) to avoid sleep disturbance of the occupants, although these levels assume that windows are open. Therefore, for closed single glazed windows a facade noise level of 55 dB (LAeq) would result in low risk of sleep disturbance within the building. However, recent WHO guidance relating to sleep disturbance by noise suggests a guideline facade noise level of 45bB (LAeq 8 hour). This level also assumes that windows may be open at night. For closed single glazing, a facade level of 55 dB (LAeq) would result in low risk of sleep disturbance within the building.

Noise criteria would apply at 1m from the facades of neighbouring noise sensitive buildings, including residences, commercial properties. Suggested noise levels are aimed not at providing noise limits for construction activities, but are proposed as criteria for the assessment for the noise impacts associated with the construction programme.

In the UK, regulators have powers (under the Control of Pollution Act 1974) to control noise from construction site through setting specific consent levels and requiring the construction company to use ‘best practicable means’ to reduce the effects of noise. The above criteria can be summarised in the tables below:

Reference is also made to ambient noise levels, particularly if night time levels are already above 45 dB (LAeq).

The noise levels set out in Table 1 are not aimed at providing noise limits for construction activities, but are proposed as criteria for the assessment of the significance of noise impacts associated with the construction programme.

Where predicted noise levels are above the criteria in Table 1, the degree of the impact can be summarised below in Table 2 (based on Institute of Environmental Management and Assessment and Institute of Acoustics Consultation Draft Guidelines for Noise Impacts Assessment – April 2002).

Industrial noise case study

A factory based in Birmingham had received a very large number of forceful complaints from local people living on a mixed residential estate built in the early-1990s. Assessments completed revealed that boundary consent levels were being exceeded regularly and substantially and that a statutory nuisance was indeed being committed. Over one hundred sources of noise were measured and the data subsequently analysed. Although some noise sources were, on the face of it, insignificant at the houses, as they were only a metre or two from the boundary they were responsible for a significant exceedance of the industrial site’s consent level.

The Local Authority agreed to suspend legal action in return for the site operator completing a comprehensive noise control programme to abate and control the noise sources affecting the houses. However, the old consent levels would be kept as insurance to ensure that the company could be challenged legally if suitable noise control progress was not made.

Noise abatement solutions were designed for all significant sources utilising additional expertise from acoustic, hydraulic, and mechanical engineers. Various abatement technologies where assessed on a cost benefit basis and a detailed programme of phased implementation and commissioning was arranged.

The noise issue was abated by 20dB(A), from a consistent nuisance to a marginal problem. Although still an issue requiring close management, the improvement has proven sufficient for all complaints to have stopped. Further improvements are scheduled for the site which will reduce the noise levels further which will ensure they not only comply with regulatory consents but also keep their neighbours happy.

Traffic noise pollution

Traffic noise is becoming a bigger issue with the rapid expansion of infrastructure in Developed and Developing nations. Some of the most intrusive noises are associated with major roads during rush hour, railways (especially those with poor rolling stock and track) and airports. The general public are acutely aware of such noises and are fiercely protective of their peace, quiet and amenity. However, for any environmental noise survey, traffic noise is generally less disturbing than industrial or leisure noise as it is typically traffic which defines the background noise for assessing noise pollution.

It is also true that predicted increases in traffic volume will not necessarily directly correlate to an increase in noise. In a typical day a busy road will be at its quietest during the middle of the day and noise will increase as the rush hour approaches. A point will come, however, when the road is so busy that traffic begins to slow-down or even stop – consequently noise levels will typically go down and vary less. Predicted increases in traffic volumes, therefore, may not necessarily lead to the noise problems that one would logically predict.

Leisure noise

Noise pollution generated by leisure activities is a very emotive problem and extremely varied in intensity and character. One person’s leisure can be another person’s nightmare if the facilities are not correctly designed and increasing trends in city centre living and mixed-use facilities make correctly designed sound insulation and effective noise management and control more important.

Activities include shooting, open air events, motor sport and football matches. Of course, the activities that cause greatest concern music, not just pop concerts and nightclubs, but home and in-car sound systems. Most people now have access to high-quality, high power, inexpensive sound systems in their homes and in their cars. The increase in sound quality means that the listener can turn the volume up far higher than ever before without any distortion. The same sound quality and intensity levels are being found in nightclubs. Modern music typically follows an intense low frequency beat, but the use of cheap building materials in nightclubs and bars can lead to a serious problem for neighbours.

However, in the UK, there are still no nationally agreed criteria governing it and standards differ widely between local authorities. Noise level standards for leisure activity-based noise are not well defined and in many cases have codes of practice set-up by each industry body. Such codes are understandably based on operational and commercial considerations so consequently have debatable objectivity.

Music noise standards vary dramatically between regulators from a simple application of the principles of BS4142, simple absolute noise limits, to inaudibility criteria stipulated within entertainment licenses used by an increasing number of authorities. For new build mixed use leisure facilities, generally standards are laid down in contracts but these can vary depending on the consultants involved. Matters are further complicated by the many different parameters for measuring noise and only trained acousticians really understand the significance of changing from one parameter to another. Some attempts have been made to set down noise assessment criteria and research is ongoing but there is still some way to go before agreement is reached on national standards.

Inaudibility is a very sensible standard to use where the circumstances suit, but contradictions with other existing guidance can occur and in these cases inaudibility needs to be technically defined. This requires the input of acoustic engineers to ensure that there is a considered and valid approach to assessing inaudibility.

Complaints to regulators in the UK continue to rise, not only due to the increased noise that exists as part of people’s day-to-day lives, but also due to the slightly confusing way in which it is regulated. This leads to site operators and other generators of noise not really knowing what they are required to do under law. The way in which noise pollution has been controlled over the past forty years has been ad-hoc, by necessity. In the UK and Europe, people are discouraged from moving into inner-city brownfield developments due to the perceived lack of noise control. These issues will become more relevant in developing countries in the coming years as the public become more protective of their amenity and aware of their civil rights. However, the UK are attempting to align and co-ordinate their policies with regards noise control in line with other EU nations, which will help ensure noise pollution is better controlled in the future.

Published: 01st Mar 2007 in AWE International