Monitoring environmental sound is an important element in managing noise impact on society. In this article, Dan Saunders, of Clarke Saunders Associates, explains some of the factors that need to be considered in the capture, measurement and accurate assessment of environmental sound.
Excessive noise can have a negative impact on health and wellbeing and is a well-recognised public health risk.
In fact, the World Health Organization places noise exposure close behind poor air quality as a health risk to the population.
Impacts on health and wellbeing include cardiovascular disease, annoyance and distractions to day-to-day activities such as reading and conversation.
The impact of noise pollution
Noise pollution has an impact on thousands of people living in the UK every day. Noise is defined as unwanted sound. It can come from a number of different sources and what may be pleasant to some people may be considered a nuisance by others.
According to the Association of Noise Consultants (ANC), the noise sources most likely to cause complaint have been identified as neighbour and domestic noise, barking dogs, transportation, construction and demolition, commercial and leisure and industrial activities.
Different people react to noise in different ways and this subjective human response means a sound source which causes extreme offence to one person may not concern another.
A noise which can be heard, and which someone considers annoying, is not necessarily a ‘statutory noise nuisance’. The judgement of what constitutes a statutory nuisance is highly contextual; there are no fixed noise thresholds for nuisance.
In assessing whether or not a noise source is sufficient to amount to a statutory nuisance, an environmental health officer has to consider the reaction of the average, reasonable person to the noise, taking account not only of its volume and character, but also factors such as when and how often the noise occurs and the duration of the noise occurrence.
The legal control on noise nuisance is by the local authority serving an abatement notice under the Environmental Protection Act 1990.
Most noise assessments require an environmental sound survey to objectively quantify the characteristics of specific activities or the soundscape of an area, whether to assess an existing or proposed potential noise source.
This is important information, and it is vital that the measurement of environmental sound is carried out by professionals who understand the nuances and variations that can be encountered, to achieve a successful outcome.
Member companies of the ANC may be able to assist with investigation of noise problems. They may also be able to provide advice to individuals or companies who have been served with a noise abatement notice.
“measurement, analysis and assessment of sound are complex scientific disciplines, which require a clear understanding of its source, propagation and perception”
They can also support businesses and organisations looking to take proactive action to act as a ‘good neighbour’ and maintain positive relations in their communities through the effective management of potential noise impacts.
A wide range of factors need to be considered as part of the noise monitoring process.
For example, a regular spike in levels could be scheduled aircraft movement. Birdsong may affect early morning levels in the summer, but not in the winter.
Fortunately, ANC members have a wealth of experience and knowledge in the consideration of the relevant factors and their potential impact on the existing and future soundscape.
One of the objectives of the ANC is ‘to maintain and, where possible, improve the standards of conduct and competence of consultants concerned with noise, acoustics and vibration’.
Companies have to fulfil strict criteria to join the Association, based on qualifications and experience, to achieve membership.
To meet the needs of a highly technical profession, the ANC regularly produces comprehensive guidance to assist practitioners in providing consistent approaches to common areas of ambiguity, while assisting others, such as clients, decision makers and members of the public.
An example of this is the ANC Green Book, which offers a guide to environmental sound measurement. This guide has recently been updated, with the second edition due out for publication shortly.
Measurement, analysis and assessment of sound are complex scientific disciplines, which require a clear understanding of its source, propagation and perception.
The importance of the baseline environmental sound monitoring cannot be overstated since the entire acoustic assessment and the subsequent design of noise control for a project will be based on the results of this exercise.
Different environments – different considerations
The Green Book sets out the various stages to an environmental sound survey, which are adapted for different circumstances.
While not prescriptive, the Green Book lists these as follows;
Scoping – this involves building a good understanding of a project before undertaking any desktop studies or measurement surveys.
While an initial scope of work may have been provided, there may be implications that the stakeholders are unaware of that would have a significant influence on the works that need to be carried out. The purpose of the acoustic assessment needs to be considered in detail at this stage. This will inform the design of the environmental monitoring survey which will be required to achieve the intended objective.
“acousticians will also consider that, in specific situations, the sound source may only occur at specific times of the day or days during a week, month or year.”
Essentially, this is a summary of the scoping process, this considers measurements as falling into three broad categories:
• Sound pressure level measurements to characterise a specific type of source
• Sound pressure level measurements to characterise an ambient climate
• Sound pressure level measurements to characterise an ambient climate and the effects of a specific type of source, i.e. the first two points in combination
It also includes consideration of the other specific requirements of the survey exercise, including time and budget constraints and site practicalities, such as access, equipment availability, project deadlines and safety.
This falls into two areas, equipment and site arrangements.
Before the survey takes place, survey equipment needs to be checked to ensure it is both fit for purpose and properly calibrated, and that it will be located and used safely.
With the preferred locations for the survey equipment already identified, when arrangements are being made for access to the site it should be checked that the site conditions will be as expected when the survey is undertaken.
This applies specifically to activities on and around the site, including traffic, construction/demolition works and operational hours of nearby land uses.
Acousticians will also consider that, in specific situations, the sound source may only occur at specific times of the day or days during a week, month or year.
This will be carefully considered in determining survey timing and duration.
The Green Book details key activities and processes to be considered on site, including health and safety requirements, identification and safety inductions.
Timings of visits and on-site locations, as well as microphone positioning, and considerations to the weather patterns and dynamic range are also detailed.
Under this subject area, the typicality of the measurement dataset is also discussed. This technical area relates to the informed judgements, which need to be made on site by an acoustics professional regarding representative description of the soundscape, including any variability and the exclusion of out of the ordinary (atypical) noise events.
“noise impact assessments need to comprise thorough surveys and properly presented analysis in technical reports by experienced, highly trained experts”
Data analysis and assessment
This is the process of inspecting, cleaning, transforming, and modelling data with the goal of highlighting useful information, suggesting conclusions, and supporting decision making.
Acousticians’ use of data analysis involves multiple facets and approaches, and encompasses a diverse range of techniques, to build an accurate picture.
Reporting and structure – The final aspect, the acoustician’s report is very often the only tangible part of the environmental noise impact assessment that the stakeholders see.
Depending on the circumstances, this can include:
• The site description (including site plan)
• Guidance, policies and Standards used
• Assessment methodology
• Measurements and noise predictions
• Results of the assessment
Noise professionals have access to a hierarchy of policy, standards and guidance documents, which are used in the assessment of noise impact, and should be clearly set out in reports. These include:
• National Policy, National Planning Policy Framework NPPF, Noise Policy Statement for England NPSE and the Noise Policy Statement for Northern Ireland
• National Planning Guidelines, Planning Advice Notes PAN (Scotland), Planning Policy Guidance, Technical Advice Note TAN (Wales & Scotland) and Circulars
• Local Authority Policies (planning, enforcement, licensing)
• British and International Standards / Codes of Practice
• Professional association guides including the ANC Green Book, as well as research papers and other published resources
They can also draw on other design guidance, standards and criteria, which can help inform the approach taken to site survey work and data gathered.
Guidance issued by the World Health Organization on community noise is also linked to a number of other UK guidance documents and standards.
In summary, noise can be a contentious issue, placed under close scrutiny by neighbours, authorities, pressure groups and others.
Noise impact assessments need to comprise thorough surveys and properly presented analysis in technical reports by experienced, highly trained experts. Environmental noise measurement is key to that – and ANC members are well-placed to support this process.