When Do You Need a Noise Impact Assessment for Planning?

If you are preparing a planning application, you may be asked whether noise could affect the proposed development or the people and businesses around it.

In some cases, the planning authority may require a noise impact assessment to help answer that question.

This is particularly common where a development will introduce a new source of noise, such as mechanical plant or commercial activity, or where new homes are proposed close to an existing road, railway, industrial site or other significant noise source.

Getting acoustic advice early can help establish whether an assessment is likely to be needed, what information should be collected and whether the design needs to change before the planning application is submitted.

What is a noise impact assessment?

A noise impact assessment looks at the existing acoustic environment, the noise associated with a proposed development and the likely effect on relevant nearby receptors.

Depending on the project, this can involve:

• measuring existing background and ambient sound levels
• identifying existing and proposed noise sources
• considering nearby homes and other noise-sensitive uses
• predicting future noise levels
• assessing the likely significance of the impact
• reviewing the layout and design of the development
• recommending mitigation where it is needed
• preparing an acoustic report to support the planning application

The scope will depend on the development. A small item of mechanical plant will require a different approach from a large residential development next to a railway, for example.

When might you need a noise impact assessment for planning?

There is no single rule saying that every planning application needs a noise assessment.

Noise is normally considered where the proposed development could generate significant noise, or where the proposed development could itself be sensitive to noise that is already present.

There are several common situations where an acoustic assessment may therefore be required.

1. New homes near roads, railways or other noise sources

Residential developments are particularly sensitive to environmental noise because people need suitable conditions both inside their homes and in relevant external amenity areas.

An assessment may be appropriate where new homes are proposed close to:

• busy roads
• railway lines
• aircraft noise
• industrial or commercial premises
• entertainment venues
• plant and machinery
• other established noise-generating uses

The assessment can help establish the existing noise environment and inform decisions about matters such as building orientation, façade design, glazing, ventilation and external amenity areas.

It is much easier to address these issues while the scheme is still being designed than after the layout has been fixed.

2. New mechanical plant

Air conditioning units, heat pumps, chillers, extract systems, fans and other building services equipment can all generate noise.

Where plant is proposed close to residential properties, the planning authority may ask for an acoustic assessment demonstrating that its operation is unlikely to result in an unacceptable impact.

This can apply to both new developments and planning applications for plant being added to an existing building.

The assessment may consider:

• manufacturer sound data
• the proposed operating hours
• distance to neighbouring properties
• screening and building geometry
• the existing background sound environment
• the character of the sound
• any acoustic mitigation that may be required

3. Industrial and commercial development

Industrial and commercial activities can introduce noise from fixed plant, deliveries, servicing, manufacturing processes and other operations.

Where this sound could affect nearby residential properties, a noise impact assessment may be needed.

BS 4142 is commonly used when assessing sound of an industrial or commercial nature affecting dwellings or other premises used for residential purposes.

It compares the sound associated with the source being assessed with the existing background sound level, while also considering characteristics such as tonality, impulsivity and intermittency, as well as the wider context.

BS 4142 should not simply be treated as a fixed planning pass or fail test. The circumstances of the site and the context in which the sound occurs are important parts of the assessment.

4. Pubs, restaurants, leisure and entertainment uses

Some developments create noise because of the activity taking place rather than simply because of mechanical equipment.

Examples can include:

• pubs and bars
• restaurants
• music and entertainment venues
• gyms
• sports facilities
• event spaces
• other evening or night-time uses

The relevant issues can include amplified music, voices, customers arriving and leaving, external areas, deliveries and building services plant.

The appropriate assessment method will depend on the particular noise source and planning context.

5. Change of use applications

A change of use can introduce a new relationship between a development and its neighbours.

For example, converting a commercial building to residential use may introduce new homes close to an existing business or significant transport noise.

Alternatively, changing premises to a restaurant, gym or other active commercial use could introduce new noise close to existing homes.

Considering acoustics at an early stage can help identify whether the proposed use is compatible with its surroundings and what design measures may be needed.

6. Heat pump installations

Heat pumps are another increasingly common reason for acoustic input.

Some installations can be carried out without a full planning application where the relevant permitted development requirements are satisfied. Others may need planning permission or additional acoustic assessment depending on the installation and circumstances.

Where noise needs to be considered, an assessment can look at the proposed equipment, its location, nearby receptors and the existing acoustic environment.

7. Developments close to existing businesses

Noise assessment is not only about protecting new development from an uncomfortable environment.

It can also be important to make sure that introducing a new noise-sensitive use does not place unreasonable restrictions on an established neighbouring business.

For example, placing new flats next to an existing music venue, industrial operation or commercial plant could create future noise issues if acoustics are not properly considered during the design.

An assessment can help the project team understand that relationship and design the new development accordingly.

Will the planning authority tell you if you need one?

Sometimes.

A local planning authority may identify a noise assessment as part of its validation requirements, during pre-application discussions or after reviewing the submitted application.

However, waiting until the planning authority requests one can result in additional work and potentially delay the application.

If noise is an obvious consideration for the site, it is often worth discussing it with an acoustic consultant before submitting the application.

Local requirements also vary, so the scope of an assessment should reflect the development, the site and the requirements of the relevant planning authority.

What happens during a noise impact assessment?

Although every project is different, the process will usually follow several stages.

Understanding the proposal

The first step is understanding what is being proposed and why noise could be relevant.

This might involve reviewing:

• site plans
• architectural drawings
• plant information
• proposed operating hours
• the surrounding land uses
• nearby noise-sensitive receptors
• the planning history or requirements for the site

Carrying out a noise survey

Where measurements are required, suitable equipment is used to establish the existing acoustic conditions at the site.

The measurement period will depend on the assessment.

Some projects may only require measurements over a relatively short representative period. Others may require unattended monitoring over one or more days to understand how sound levels change between daytime, evening and night-time periods.

Weather conditions, measurement locations and the sources contributing to the acoustic environment also need to be considered.

Assessing the proposed development

The measured data can then be considered alongside information about the development.

Depending on the project, this could involve calculations or computer noise modelling to predict how sound will travel between a source and the relevant receptors.

The assessment method should be appropriate to the particular source and planning question rather than applying the same standard to every project.

Developing mitigation

If the assessment identifies a potential noise issue, that does not necessarily mean the development cannot proceed.

There may be practical ways to reduce the impact.

These could include:

• changing the site layout
• increasing distance between the noise source and sensitive receptors
• selecting quieter plant
• relocating equipment
• introducing acoustic screening or enclosures
• improving the acoustic performance of the building envelope
• considering ventilation strategy
• changing operating arrangements
• using buildings themselves to provide screening

The best solution is often one that is incorporated into the design rather than added at the end of the project.

What should a planning noise report contain?

The exact content will depend on the project, but a noise impact assessment report will typically explain:

• the proposed development
• the site and surrounding area
• the relevant noise sources and receptors
• how the noise survey was undertaken
• the equipment and measurement methodology used
• the measured acoustic conditions
• the relevant guidance or assessment methodology
• any calculations or modelling undertaken
• the predicted noise impact
• important assumptions and uncertainties
• any mitigation measures required
• the conclusions of the assessment

A useful report should do more than present tables of sound levels. It should explain what the results mean for the proposed development and provide the project team with clear, practical recommendations.

Which standards are used for a noise impact assessment?

There is no single British Standard that applies to every planning noise assessment.

The appropriate guidance depends on the type of development and the noise being assessed.

For example, BS 4142:2014+A1:2019 is commonly relevant where industrial or commercial sound may affect residential premises.

Other standards and guidance may be appropriate for environmental noise, residential development, building services, construction activity or other particular sources.

National planning policy and guidance also provide the wider framework within which noise is considered by planning authorities.

An acoustic consultant should therefore establish the appropriate assessment approach for the individual project rather than selecting a standard simply because it is familiar.

Can a noise assessment guarantee planning permission?

No.

A noise assessment provides technical evidence to help the planning authority make its decision. It cannot guarantee that planning permission will be granted.

Noise will also usually be only one of several matters considered as part of the application.

What a good assessment can do is identify potential acoustic issues, quantify them where appropriate and demonstrate how they can be addressed through the design or suitable mitigation.

When should you appoint an acoustic consultant?

Ideally, before noise becomes a planning problem.

On some projects, the acoustic work is straightforward. On others, the findings can affect the layout of the development, façade specification, ventilation strategy, plant selection or equipment location.

Early involvement gives the design team more options.

It can also prevent situations where an assessment is commissioned shortly before submission and identifies a problem that would have been much easier to resolve earlier in the design process.

Do I need a noise impact assessment for my project?

You may need one if:

• your development will introduce a new source of noise
• you are installing mechanical plant near homes
• new residential development is proposed in an existing noisy environment
• the site is close to industrial or commercial activity
• you are making a change of use application
• the proposal includes an entertainment, leisure or other potentially noisy use
• the local planning authority has requested an acoustic assessment
• noise could otherwise be a material issue for the development

If you are unsure, it can be worth checking before commissioning a full survey. In some cases the requirements can be established from an initial review of the proposal and site.

Noise impact assessments from auricl

auricl provides noise surveys, assessments and practical acoustic advice for developments across the UK.

We work with developers, architects, planning consultants and project teams to establish what acoustic work is needed, carry out appropriate surveys and assessments, and explain the results clearly.

Where noise mitigation is required, our focus is on finding practical measures that work with the wider design of the project.

Planning a development where noise could be an issue?

Tell us what you’re working on and we’ll suggest the right next step.