How Does Noise Mapping Work?

A noise map shows how sound levels vary across a site, building façade or wider area.

It usually uses coloured bands or contour lines to make predicted sound levels easier to understand. This can help a project team identify where noise is highest, which buildings or spaces may be affected and whether a proposed control measure is likely to work.

Noise maps can be used to assess:

• Road, rail and aircraft noise
• Industrial and commercial sites
• Building-services plant
• Construction activity
• Deliveries and vehicle movements
• Entertainment noise
• New residential developments
• Acoustic barriers
• Alternative site layouts

Although the final map looks simple, producing a reliable one requires suitable source data, a carefully constructed acoustic model and professional judgement about how the results should be interpreted.

What is a noise map?

A noise map is a visual representation of measured or predicted sound levels.

For a typical development project, the map may be overlaid onto:

• A site plan
• An aerial image
• A topographical survey
• A proposed development layout
• A building elevation
• A three-dimensional site model

Different colours usually represent ranges of sound level.

For example, one colour may show areas within a particular decibel band, with other colours showing progressively higher or lower levels.

The map may also identify:

• Individual receiver positions
• Nearby homes
• Proposed buildings
• Noise sources
• Acoustic barriers
• Plant equipment
• Roads and vehicle routes
• Different assessment scenarios

A noise map helps people see patterns that can be difficult to understand from a table of numbers alone.

Is a noise map measured or predicted?

It can be either, but most detailed project noise maps are based primarily on acoustic modelling.

It would rarely be practical to measure the sound level at every point across a site. Measurements only describe conditions at the microphone positions and during the times when the survey took place.

A computer model can calculate sound levels across a much larger grid.

The model may use:

• Measurements from a noise survey
• Manufacturers’ plant data
• Sound power levels
• Traffic-flow information
• Train movements
• Aircraft data
• Operating hours
• Construction plant schedules
• Published source data
• Proposed building and site layouts

The measurements and source data are then combined with information about how sound will travel through the environment.

The resulting map is a prediction based on the inputs and calculation method used. It is not a direct measurement at every coloured point.

What does a noise map show?

A noise map can show several different types of information.

Sound-level contours

The most familiar output is a set of coloured sound-level contours.

Each contour represents a range of predicted sound levels across the site.

This may help identify:

• The noisiest parts of the site
• Quieter areas
• How far sound is likely to travel
• Which properties may receive the highest levels
• Whether a building provides useful screening
• How a barrier changes the predicted result

The contours normally represent a defined sound metric and assessment period.

The title and key should explain exactly what is being shown.

Individual receiver levels

A model may calculate results at specific receiver points rather than, or in addition to, a continuous grid.

These receivers may represent:

• Bedroom windows
• Living-room windows
• Gardens
• School façades
• Offices
• Hotel rooms
• Existing homes
• Proposed homes
• Monitoring locations
• Planning assessment positions

Results can be calculated at different heights to reflect different floors of a building.

This is important because a ground-level barrier may protect a garden or lower-floor window while providing much less screening to upper floors.

Façade noise levels

A façade map shows predicted sound levels across the outside of a building.

This can help the design team understand:

• Which elevations are most exposed
• How sound varies by floor
• Which rooms should be positioned on quieter façades
• Whether different glazing specifications are needed
• Where alternative ventilation may be required
• Whether balconies or façade features affect the result

Façade mapping can be particularly useful for residential developments exposed to road, rail, aircraft or commercial noise.

Vertical sections

A vertical noise map or cross-section can show how sound changes with height.

This can help assess:

• Roof-mounted plant
• Tall acoustic barriers
• Multi-storey buildings
• Elevated roads or railways
• Upper-floor receivers
• Cuttings and embankments
• Noise moving over or around buildings

A plan view alone may not show these relationships clearly.

Scenario comparisons

Noise mapping can compare different versions of a design.

For example:

• Existing conditions
• Proposed conditions
• With and without a barrier
• Different barrier heights
• Alternative plant locations
• Different operating hours
• Different site layouts
• Alternative building orientations
• Different construction phases
• Several mitigation packages

Using the same calculation settings for each scenario allows the project team to see how a change affects the predicted result.

What sound metric does a noise map use?

A noise map must be labelled with the sound metric and time period it represents.

Depending on the source and purpose, this could include:

• An equivalent continuous sound level over a stated period
• Daytime sound
• Evening sound
• Night-time sound
• A plant sound level
• A construction phase
• A maximum sound level
• A rating level
• A long-term strategic noise indicator

Different metrics answer different questions.

A daytime average cannot automatically be used to describe night-time conditions. A maximum event level is not the same as an average level, and a BS 4142 rating level includes considerations that are not shown by a simple source level alone.

The correct metric depends on:

• The noise source
• The assessment method
• Planning requirements
• The sensitivity of the receiver
• The time of day
• The purpose of the map

Does a noise map show different frequencies?

Most planning and environmental noise maps show an overall sound-level metric rather than separate high- and low-frequency contours.

However, acoustic models may calculate sound in individual frequency bands before combining the results.

Frequency data can be important when assessing:

• Tonal plant
• Low-frequency equipment
• Barriers
• Enclosures
• Façade performance
• Attenuators
• Sound insulation
• Long-distance propagation

A separate frequency-specific analysis may be needed where the character of the sound is important.

The colours on a standard noise map should not be assumed to represent different frequencies unless the key explicitly says that they do.

What information goes into a noise model?

The quality of a noise map depends heavily on the quality of its inputs.

Noise-source information

The model needs suitable information about each sound source.

This may include:

• Sound power level
• Frequency spectrum
• Source height
• Position
• Direction
• Operating time
• Number of events
• Movement route
• Speed
• Whether it is continuous or intermittent
• Whether several sources operate together

For mechanical plant, the information may come from manufacturers’ data, measurements or calculations.

For construction activity, the model may use plant schedules, operating durations and recognised source data.

For roads or railways, the input may include vehicle or train numbers, speeds, types and movement patterns.

Site geometry

The model needs an accurate representation of the site and surrounding area.

This may include:

• Buildings
• Walls
• Barriers
• Embankments
• Cuttings
• Roads
• Railways
• Ground levels
• Roof heights
• Source heights
• Receiver heights
• Openings
• Façades

The Environment Agency’s modelling guidance requires detailed information about sources, receptors, buildings, barriers and terrain where computer modelling supports a noise impact assessment.

An incorrect building height or missing barrier can materially affect the result.

Ground conditions

Sound can behave differently over hard and soft ground.

The model may account for surfaces such as:

• Concrete
• Tarmac
• Water
• Grass
• Soil
• Mixed ground
• Industrial yards

Ground effects can influence how sound reduces with distance, particularly over longer propagation paths.

Screening and diffraction

Buildings, barriers and terrain may interrupt the direct path between a source and receiver.

Sound does not disappear completely when the line of sight is blocked. It can travel over and around the obstacle.

The model therefore considers diffraction around:

• Acoustic fences
• Earth bunds
• Buildings
• Walls
• Embankments
• Other solid structures

The effectiveness of a barrier depends on its height, length, position and construction.

A short or poorly positioned fence may provide little useful benefit, even if it looks substantial on plan.

Reflections

Hard surfaces can reflect sound.

Relevant reflecting surfaces may include:

• Building façades
• Retaining walls
• Solid barriers
• Courtyards
• Large areas of hard construction

A barrier may reduce sound in one direction while reflections from surrounding surfaces influence the result elsewhere.

The model settings should reflect the level of detail required by the assessment.

Weather and atmospheric conditions

Outdoor sound propagation can be influenced by:

• Wind direction
• Wind speed
• Temperature
• Temperature gradients
• Humidity
• Atmospheric stability

The calculation method may represent conditions that are favourable to sound travelling from the source to the receiver.

ISO 9613-2:2024 provides an engineering method for predicting outdoor environmental sound under defined propagation conditions. It uses information about source strength, geometry, ground conditions and other attenuation effects. It does not apply to aircraft in flight or blast waves.

The appropriate calculation method depends on the source and assessment.

Buildings and receivers

Buildings can act as both barriers and receivers.

The model may need to represent:

• Building height
• Façade position
• Number of storeys
• Windows
• Sensitive rooms
• Reflections
• Shielding
• Courtyards
• Balconies

Receivers should be positioned where the assessment needs to understand the sound level.

A model that only calculates levels at convenient open locations may miss the people or rooms that matter most.

How is a noise map created?

A typical process involves the following stages.

1. Define the purpose of the assessment

The first step is to establish what the map needs to show.

Questions may include:

• Is the development generating noise?
• Is the development sensitive to existing noise?
• Which source needs to be assessed?
• Which period matters?
• Which receptors need to be protected?
• Is the map supporting planning, design or operational management?
• Which assessment method applies?
• Which scenarios need to be compared?

A map created without a clear purpose can become visually impressive but technically unhelpful.

2. Review the site and proposal

The consultant reviews:

• Site plans
• Topographical data
• Building layouts
• Plant schedules
• Operating hours
• Transport information
• Planning requirements
• Nearby properties
• Existing acoustic reports
• Proposed construction phases

This helps determine what information is available and what needs to be measured or confirmed.

3. Carry out a noise survey where needed

Measurements may be required to:

• Establish existing conditions
• Measure a current source
• Validate plant data
• Determine background sound levels
• Understand changes by time of day
• Check a completed model
• Investigate an existing complaint

The survey should be designed around the assessment.

Long-term monitoring is useful in some situations, but it is not automatically necessary for every noise map.

4. Build the digital site model

The consultant imports or creates the relevant geometry.

This may include:

• Ground contours
• Buildings
• Sources
• Receivers
• Roads
• Railways
• Barriers
• Proposed development
• Existing development

The level of detail should be proportionate.

A model does not need every small architectural feature, but it must include the elements that may materially influence sound propagation.

5. Enter the source data

Each noise source is added with suitable acoustic and operating information.

A source may be represented as:

• A point
• A line
• An area
• A building façade
• A movement route
• A road or railway
• A group of equipment

The representation should match how the source behaves.

6. Select the calculation method

The calculation method should suit the source and assessment.

Different methods may be used for:

• Industrial plant
• Road traffic
• Railways
• Aircraft
• Construction
• Wind turbines
• Entertainment activity

The method, software settings and assumptions should be recorded clearly.

7. Run the calculations

The software calculates sound propagation from each source to the grid and receiver positions.

This may account for:

• Distance
• Geometrical spreading
• Air absorption
• Ground effects
• Screening
• Diffraction
• Reflections
• Source directivity
• Operating time
• Meteorological assumptions

Where several sources operate together, their contributions are combined logarithmically rather than added arithmetically.

8. Check and validate the model

The model should be reviewed before its results are relied upon.

Checks may include:

• Comparing predictions with site measurements
• Reviewing source data
• Checking source and receiver heights
• Confirming building geometry
• Reviewing terrain
• Checking barrier continuity
• Testing sensitivity to assumptions
• Comparing output with hand calculations
• Reviewing unexpected contour patterns

A colourful map is not evidence that the model is correct.

The underlying data, assumptions and validation are more important than the appearance of the output.

9. Produce and interpret the outputs

The consultant selects outputs that answer the project question.

These may include:

• Contour maps
• Façade maps
• Receiver tables
• Vertical sections
• Scenario comparisons
• Difference maps
• Mitigation maps

The report should explain:

• What the map represents
• Which sources are included
• Which period is shown
• The calculation method
• The assumptions
• The limitations
• The relevant criteria
• What the result means for the project

What is 3D noise mapping?

The term 3D noise mapping usually refers to a three-dimensional acoustic model of the site.

The model contains heights and spatial relationships for buildings, sources, barriers, terrain and receivers.

The outputs may still be presented as two-dimensional plans because they are easier to read.

A three-dimensional model can also produce:

• Façade grids
• Vertical sections
• Views at different heights
• Multi-storey receiver results
• Three-dimensional visualisations

The term should not be taken to mean that every project needs a complex animated model.

The appropriate output is the one that communicates the result clearly and supports the design decision.

When is noise mapping useful for planning?

National planning guidance says noise should be considered where a development may create additional noise or would be sensitive to the existing acoustic environment. It also recommends considering good acoustic design early so appropriate and cost-effective solutions can be identified from the outset.

Noise mapping may help where:

• Homes are proposed near a busy road or railway
• A development includes new industrial or commercial activity
• Mechanical plant is close to nearby residents
• A mixed-use scheme contains noisy and sensitive uses
• A large site has several possible layouts
• Different mitigation options need to be tested
• Noise varies significantly across a site
• Upper floors receive different levels from ground-floor areas
• A planning authority requests predicted noise information

A noise map is not required for every planning application.

The appropriate evidence depends on the proposal, location, noise source and local authority requirements.

Some projects may only need calculations at a few receiver positions. Others benefit from full contour and façade mapping.

Noise mapping for residential development

Noise mapping can help identify which parts of a site are most exposed to transport, industrial or commercial noise.

The design team may use the results to consider:

• Building orientation
• Apartment layouts
• Bedroom locations
• Façade performance
• Glazing
• Ventilation
• Balconies
• Gardens
• Courtyards
• Acoustic barriers

A map can show where layout changes may reduce exposure before the design relies on upgraded building fabric.

For example, placing less sensitive rooms on a noisier façade may help protect bedrooms and living spaces.

Noise mapping for industrial and commercial sites

An industrial or commercial model may include:

• Fixed plant
• Mobile equipment
• Loading areas
• Deliveries
• Internal site roads
• Openings in buildings
• Roof and façade breakout
• Operating hours
• Acoustic barriers
• Nearby homes

The model can identify which sources contribute most at each receiver.

This helps focus mitigation on the equipment or activity that matters rather than treating every source equally.

Where modelling supports an Environment Agency noise impact assessment, the submitted information may need to include model assumptions, source sound-power data, operating times, buildings, barriers, terrain and receptor results.

Noise mapping for building-services plant

Noise mapping may be used to assess:

• Air-conditioning units
• Air-handling equipment
• Chillers
• Heat pumps
• Generators
• Transformers
• Refrigeration equipment
• Exhausts and air intakes
• Roof-mounted plant

The map can compare:

• Different equipment locations
• Screen heights
• Enclosures
• Attenuators
• Operating scenarios
• Day and night conditions

The result may support a BS 4142 assessment where industrial or commercial sound affects nearby residential premises.

However, the map itself does not replace the full assessment of sound character, context and uncertainty.

Noise mapping for construction

A construction noise model may represent different phases of the work.

These could include:

• Demolition
• Earthworks
• Piling
• Concrete works
• Façade installation
• Road construction
• Night-time activities

The model may use the planned equipment, operating durations and locations for each phase.

It can help the team:

• Identify the noisiest phases
• Review working methods
• Position temporary barriers
• Plan equipment locations
• Compare alternative sequences
• Identify monitoring locations
• Communicate likely effects

Construction activity changes frequently, so the model needs realistic assumptions rather than treating every machine as operating at maximum output in one fixed location throughout the project.

Can noise mapping test acoustic barriers?

Yes.

A model can compare predicted sound levels:

• Without a barrier
• With different barrier heights
• With alternative positions
• With an earth bund
• With buildings providing screening
• With several control measures combined

The effectiveness of a barrier depends on whether it interrupts the sound path.

Important factors include:

• Height
• Length
• Proximity to the source or receiver
• Gaps
• Ground levels
• Upper-floor receivers
• Construction
• Reflections
• Alternative sound paths

A barrier that helps at ground level may provide limited protection to a taller building.

Noise mapping helps show this before construction.

Can noise mapping help choose a site layout?

Yes.

Layout can be one of the most effective forms of noise control.

A map can help the design team consider:

• Moving buildings away from a source
• Using less sensitive buildings as screens
• Creating protected courtyards
• Relocating plant
• Reorienting loading bays
• Moving access roads
• Protecting gardens
• Positioning bedrooms on quieter façades
• Separating noisy and quiet uses

Planning guidance identifies layout, engineering controls, conditions and insulation as broad ways of mitigating noise.

Using layout first may reduce the need for heavier façades, tall barriers or operational restrictions later.

Strategic noise maps and project noise maps

The term “noise mapping” is also used for large-scale strategic maps produced by public authorities.

These are different from a detailed model prepared for one planning or design project.

Strategic noise maps

Strategic maps cover large areas and major sources.

In England, Defra’s 2022 round-four strategic mapping provides estimated road and rail noise for 2021. The data was produced under the Environmental Noise (England) Regulations 2006 to help identify and prioritise areas for potential action.

Strategic maps may be useful for:

• Policy
• Transport planning
• Noise action plans
• Initial site reviews
• Research
• Identifying broad areas of exposure

They are designed to provide a large-scale overview.

Project-specific noise maps

A project map is normally more detailed and tailored to a particular proposal.

It may use:

• Current site measurements
• Detailed building geometry
• Proposed plant
• Local topography
• Specific receivers
• Alternative layouts
• Project-specific mitigation

A strategic map should not automatically be used as a substitute for a detailed site assessment.

The datasets, source assumptions, dates and level of detail may not match the needs of the project.

Are noise maps completely accurate?

No model predicts the future with complete certainty.

A noise map is only as reliable as:

• The source data
• The site geometry
• The calculation method
• The operating assumptions
• The weather assumptions
• The survey data
• The model settings
• The consultant’s interpretation

Possible sources of uncertainty include:

• Equipment that has not yet been selected
• Changing operating patterns
• Incomplete manufacturers’ data
• Future traffic levels
• Changes to the site layout
• Construction tolerances
• Simplified building geometry
• Variation in weather
• Uncertain source directivity
• Unknown façade openings
• Several sources operating unpredictably

A good report should make important assumptions and uncertainties visible.

The model should be detailed enough to support the decision without suggesting a level of precision that the available information cannot justify.

Does noise mapping include vibration?

Not normally.

Noise and vibration are related but different.

A noise map predicts sound pressure levels through the air.

A vibration assessment may consider:

• Ground-borne vibration
• Structure-borne vibration
• Human response
• Building damage risk
• Re-radiated sound inside buildings
• Sensitive equipment

Different measurement methods, prediction approaches and criteria may apply.

A project involving railways, piling, machinery or heavy construction may need both noise and vibration assessment, but the results should not be presented as though they are the same thing.

Common mistakes in noise mapping

Common problems include:

• Treating a map as a direct measurement at every point
• Using poor or unverified source data
• Omitting important buildings or terrain
• Using incorrect source heights
• Ignoring upper-floor receivers
• Applying the wrong calculation method
• Failing to record assumptions
• Showing contours without explaining the metric
• Using an assessment period that does not match the activity
• Assuming a strategic noise map is detailed enough for a planning application
• Treating different colours as different frequencies
• Modelling every source at full output without a realistic operating scenario
• Assuming a barrier will work without checking its geometry
• Producing attractive graphics without validating the calculations
• Presenting the result as more precise than the available data allows

What should a noise-mapping report include?

A clear report should normally explain:

• The purpose of the assessment
• The site and proposal
• The sources included
• The receivers assessed
• Survey information
• Source data
• Operating assumptions
• Calculation method
• Model settings
• Site geometry
• Ground and weather assumptions
• Mitigation
• Uncertainty
• Validation
• The meaning of each map
• The consultant’s conclusions
• Recommended next steps

The map should support the explanation rather than replace it.

Readers should be able to understand what was modelled and why the results are relevant.

Why use an acoustic consultant for noise mapping?

Noise-mapping software performs calculations, but it does not decide whether the model is suitable.

An acoustic consultant needs to determine:

• Which sources matter
• What needs to be measured
• Which calculation method applies
• Which time period should be modelled
• Where receivers should be placed
• Which assumptions are reasonable
• How the model should be validated
• Which criteria are relevant
• What the results mean
• Which mitigation is practical

Auricl uses noise and vibration surveys alongside three-dimensional modelling to support planning and detailed design. Its team also has specific experience with noise-mapping software.

The objective is not simply to produce a colourful plan. It is to give the project team useful evidence that supports a decision.

Talk to auricl about noise mapping

If your project needs noise modelling for planning, design or mitigation, tell us about the site, the proposed activity and the surrounding area.

We can advise whether noise mapping is appropriate, identify the information required and explain the results clearly.