All settings are stored in the URL. This is updated every time you make a change.
Noise Mapping Tool
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Disclaimer - please note:
It is important to read through this guide before using this tool or its calculations. By using the model you are accepting our terms of use.
Introduction
What is this noise mapping tool?
The dBmap.net Noise Mapping Tool is used for modelling sound levels using sources of noise and screening from barriers. This is intended to be a tool for understanding and implementing the calculations of ISO-9613 and creating interactive models that are freely accessible.
Please read through this guide. You can print this page and you can access it again at any time from within the Global Settings sidebar.
Software that runs in the browser
Save your model by bookmarking the page or share the link. Click here for more information
The browser back button will "undo" changes.
Computer requirements
Any up-to-date web browser. Calculation times will depend on the processing power of your device.
This tool is free to use. Some features are only available when you are logged into a user account with a valid subscription.
Get started
Configure your model
The top right button is where you can access the Global Settings sidebar panel. Here you will find all the options for your model including configuration settings based on the calculation parameters of ISO9613.
In there you will also find the button to open up this guide.
Tools for editing
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Select
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Pan
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Zoom
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Edit Objects
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Draw Grid
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Draw Section *
Cross Section mode
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Add Objects
Objects
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Point Source
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Line Source *
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Barrier
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Building
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Receiver
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Ray-Receiver
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Accessory Line
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Image
* Subscription only
Calculating levels
Calculations are automatically run whenever a change is made to the model. You can temporarily pause this process by clicking the top left button.
To stop these calculations permanently, under Global Settings change Display to "Grid off".
Multi-thread calculations Subscription only
You can speed up calculations by enabling multi-thread calculations. This will utilise more cores of your CPU for faster processing.
Saving and sharing
How to save the model
All the settings for the model are stored in the URL in the location bar which means you can simply bookmark the web page and it will save your model exactly as it is.
Remember to create a new bookmark or update the old one whenever you make any further changes.
Stored in your browser history
Each change you make creates a new entry in your browser history, which means you can undo your changes simply by hitting the back button or going back through the history.
Export results
In the Global Settings sidebar there are various Export options:
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Report (PDF) Subscription only
Generate a PDF of the noise model based on the active mode and current view. Includes tables and charts of receiver levels, spectrums and breakdown of sources.
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Grid image (PNG)
Download an image of the grid. Subscribers export higher resolution images. To download the Cross Section, Ground Heights or 3D view, activate this mode first.
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Receiver calculations in detail
Create a comma-separated file to load into spreadsheet software. All objects are detailed in full and each receiver has a detailed list of sources including calculation breakdown.
Sharing the model
As with saving, you can share the link and other users can view your model exactly as you have set it up at that moment. Their browser may be different and may recalculate at a different speed but the results will be the same.
The URL is too long!
Click the Short URL button in Global Settings. This will use our server database to store your configuration and automatically convert it to a short URL.
Snapshots feature Subscription only
Subscribers can take Snapshots that saves the short URL to their account with a thumbnail of their model.
What about sharing to non-subscribers?
Users who are not logged-in or do not have a valid subscription will not be able to access the subscription-only features, however any line sources and ground heights that you have added to the model will still be included.
Inspecting the model
Using a ray-receiver to inspect the calculated levels
The ray-receiver illustrates the sound paths considered.
These include:
- Example A Direct paths are drawn from all sources
- Example B Black dots mark barrier intersections
- Example C Red dots indicate the ISO barrier attenuation limit has been reached on some or all of the frequency bands (when the limit is enabled)
- Example D Grey dots indicate that the barrier does not shadow the receiver and is below the line of sight
- Example E When set to "waves" the rays will illustrate the wavelength of the source
- When set to "rays" for broadband sources, each dash represents one single frequency band
- Example F Reflected paths when reflections are enabled and screens are considered as reflecting. In the example, not all frequency bands are reflected causing gaps in the dashed line
- Example G Paths considered around vertical edges of screens are illustrated in blue (when enabled in settings)
Ray-receiver examples
Ground height topography Subscription only
Ground height objects are only visible in Ground Height mode.
Ground height objects
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Height Point
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Height Line
Triangulation and screening ground
Ground height is triangulated using the height points and lines. The ground is sloped in locations where only two height points are available.
When "Draw ground height triangulation and screening" is selected in the Global Settings, the resulting ground height triangles are drawn onto the grid and the edges that can cause screening are highlighted in white.
Screening ground is highlighted in white
Barrier heights over sloping ground
When placed on sloping ground, the model considers one end of a flat barrier or one corner of a building as the reference point for the height.
When in Ground Height mode each building and barrier has a basic wireframe of the 3D shape to illustrate the difference in height at each point.
Example of the building wireframe in Ground Height mode
Change the height reference point
Hover over the object and Click the centre point to shift the reference point to the next available location.
Cross section Subscription only
Mapping the vertical plane
Cross Section mode allows you to slice through your model and see the vertical location of objects.
Example of the cross section line
Quick-select a cross section
In this mode, click on the following to quickly set the cross section line to fit:
- Barrier/Building face or 1m facade (depending on settings). This also sets the cross section height to match
- Sound ray drawn by a ray-receiver
- Accessory line
Pop-up window
Control the cross section elevation by dragging the top edge of the pop-up window.
Dragging either side of the window will rescale the cross section grid.
Control object display
Lines that intersect the section line and points within the capture area (1 metre) will appear.
Click the eye icon to view the projection of all objects and sound rays upon the vertical plane.
The grid icon will toggle displaying the horizontal grid height.
3D view Subscription only
View your model in 3D space in a pop-up window
The Compass indicates the direction of view. Click to reset the view orientation.
Rotate the view either with the set direction buttons or Click and drag the window using your mouse.
Navigate from the main area using the Pan tool or by repositioning the 3D view centre point. Alternatively, use the right button or arrow keys in the pop-up window.
Centre point shown in the main window
Toggle displaying the horizontal and vertical grids.
Sound levels for sources
What is a sound power level?
Receivers (e.g. sound level meters) measure the "sound pressure level" (Lp), a decibel value of the sound by a source at a distance.
The source of sound itself is calculated with a "sound power level" (Lw). This is a decibel value that represents the total acoustic output radiated.
They both contain frequency and amplitude information, but the difference is that a sound power level does not include distance information.
Calculating a sound power level
If you have a distance included with your decibel level, the decibel figure may represent a sound pressure level. You can use this to calculate the sound power level using the following calculator.
Sound pressure to sound power calculator
dB
m
dB
Frequency information
If you have only a single decibel figure for your sound power and it is for a broadband source, put it in at 500Hz as instructed in ISO9613-2.
The scope of ISO9613-2 only covers the octave bands 63 Hz to 8 kHz. The 31.5 Hz and 16 kHz octave bands are not officially supported by ISO9613-2 but are made available in the model for use, utilising the parameters of the adjacent octave band where necessary.
Leq or Lmax?
Useful for modelling sound sources that are not consistent, the Leq or "equivalent continuous sound level" is a single value that represents the equivalent amount of energy in a given period for a fluctuating source as if it were a steady continuous noise level. For this reason the Leq is always accompanied with a reference to the length of time that it represents.
The Lmax is a maximum level (based on the standard time-weightings: fast, slow or impulse) and is useful for modelling the peak of a noise source, such as a vehicle pass-by.
Sound energy from line sources Subscription only
For a point source, sound radiates in a sphere and the "sound power level" represents the total sound energy. A line source radiates as a cylinder along the section lengths and the sound power level is usually considered by the sound energy per metre of length. Therefore, the sound power values are different to a point source and are not directly interchangeable.
When the model calculates a line source, it breaks the line into segments with a point source at the centre with a level proportional to the length of this segment. Use a ray-receiver to inspect this behaviour.
Limitations and assumptions
Assumptions used in calculations
- Noise sources behave as a point (or line for line sources) and are far-field, where inherent directivity is minimal.
- The ground is of a continuous type (a single ground factor)
- Screens are flat with no significant transmission of sound through or under the screen. i.e. not floating above the ground or with empty sections / perforations.
Suitable meteorological conditions
Sound propagation is affected by variations in meteorological conditions. Below are suitable conditions taken from ISO9613-2.
- Moderate downwind propagation. This is defined as a wind direction within an arc of 90 degrees with the wind blowing from source to receiver.
- Wind speed between approximately 1-5 m/s, measured 3-11 m above the ground.
- A moderate ground-based temperature inversion, such as is common on clear, calm nights should not significantly affect accuracy.
- Alternatively, the average of varying meteorological conditions over months or years.
For more information about the calculations and their limitations, refer to ISO9613 parts 1 and 2.
Accuracy
It is essential to consider that modelling is only ever an estimate and real-world measurements may differ greatly.
The following table of accuracy is taken from ISO9613-2 based on tests without screening or reflections
| Average height of source and receiver | Distance between source and receiver | |
|---|---|---|
| 0 - 100m | 100m - 1km | |
| 0 - 5m | +-3dB | +-3dB |
| 5 - 30m | +-1dB | +-3dB |
Degree of error
Computer modelling requires a simplification of real-world conditions into basic components. For each simplification there will be a degree of error added to the model. It is recommended that you highlight where these simplifications have taken place.
Vertical edge diffraction
When enabled, lateral paths around vertical edges are found within a flat plane inclined along the direct source-to-receiver line.
Illustration of the inclined source-to-receiver plane
Convex path option
The lateral path method can be configured to only consider "convex" paths that curve in a single direction and do not zig-zag.
Convex path illustration
Limit distance (ISO recommendation)
ISO17534-3 recommends that lateral paths are limited to vertical edges within the range of the most distant horizontal edge multiplied by 8, with respect to distances from the direct source-to-receiver line. In complex models, applying this recommendation will improve calculation times considerably.
Vertical edges must be shadowing
ISO9613-2 considers the effect of edges that are not screening, for example an observer looking over the top of a wall. This model only accounts for such a situation along the top edges. Vertical edges are only considered when you are in the shadow of the barrier.
Inspect the sound paths
It is recommended to use a ray-receiver to inspect vertical paths and decide yourself the importance of these diffracted levels. Read here for more information on using the ray-receiver
Parameters in detail
Ground Factor
Sound waves will be reflected or absorbed by the ground depending upon the frequency of the sound wave and how porous the ground is (indicated by the "Ground factor" value G). The barrier attenuation formula also accounts for ground effects.
- For "Hard Ground" G = 0. Hard ground reflects sound waves. Examples include roads and paved areas.
- For "Soft Ground" G = 1. Soft ground is porous and absorbs sound waves. Examples include grass, trees and other vegetation.
- For "Mixed Ground" use a value for G between 0 and 1 that represents the fraction of the ground that is soft.
Plot the ground factor results
Barrier Attenuation
ISO barrier attenuation limit (20/25dB)
Insertion of a screening barrier will reduce the level of a source using the formulae of ISO9613-2. The guidance states that this reduction in any octave band is limited to 20dB in the case of a single screen or 25dB for two screens. ISO9613-2 only considers up to two screens, the two that are most effective, and all others are ignored.
You may want to disable this limit to see what effect it has on the final levels.
ISO check barrier perpendicular dimension > wavelength
A barrier is only considered to be screening if the horizontal dimension perpendicular to the source-to-receiver line is greater than the wavelength.
You may want to disable this check to explore the unusual effect it causes. For example, as you move around a barrier its apparent width in your field of vision decreases. There will be a point where this width drops below the wavelength of the source and the barrier will no longer be considered to be screening.
Screening Ground
Screening ground reflections
In the formulae of ISO9613-2 (1996) ground effects are removed by the insertion of a barrier. However, ISO17534-3 (2015) recommends that only negative ground effects are removed - i.e. attenuation due to ground absorption.
When "Do not screen ground reflections" is selected, any increase in level due to ground effects will not be affected by barrier insertion, as is recommended.
Ground as a barrier
Raised ground levels will behave as a barrier when breaking the line-of-sight between source and receiver. Read here for more information about inspecting ground level screening
Reflections
Reflections
Screens with a reflection coefficient above 0.2 are considered to be reflecting and the model will include these reflected sources in up to two screens when First and Second reflections are enabled in the settings. Barrier attenuation along the reflected path is also considered up to the height of the reflecting screen.
Only barrier and building sides make up the reflecting surfaces considered. Reflections from the roof of a building are not considered. Ground reflections are part of the ground effect calculation (ground factor).
Reflected level in dB
This is the reduction in level applied to the original sound level based on the chosen reflection coefficient.
Facade level (1m)
A "facade level" measurement is one taken at 1 metre perpendicular distance from a large reflecting surface. It is an industry practice for measurements that can be later adjusted to a free-field measurement, one that is outside of the range of influence of reflecting surfaces. The behaviour of reflections at less than 1m from the facade are not accounted for.
By enabling this all buildings and barriers will show a dashed line illustrating the 1m facade location. Reflections are only considered at distances beyond this line. Additionally, receiver points will be kept outside of this area when being positioned.
ISO reflector surface size check
For a surface to be considered as reflecting, the size of the surface is compared to the wavelength of the sound using a formula that also considers the angle of incidence and sound path length. This formula can be found in the guidance.
You may want to disable this check to see the result when reflections are always considered for a vertical surface regardless of its size.
Terms of use and your privacy
Rights over using the model
The model is free to use for both private and commercial use but without any warranty.
This is an approximate calculation tool to assist in understanding acoustics and noise mapping (sound level modelling).
It should not replace your own calculations and real life measurements.
Privacy - what information is online?
The settings of the model are stored in the URL. This is loaded from our server when you or someone else first loads the model from the URL and each time the URL shortening service is used. As the settings are stored in the URL, anyone with access to the URL will have permanent access to these settings.
Google Analytics is used to track page visits.
We may sometimes use information about the general activity of the model to improve the service but we treat all modelling activity as confidential and will not pass this information on to third parties.
The User Subscription service stores your account settings and library (snapshots, colour schemes, sound levels and images) in our database. This data is never made available to other parties or used for any purpose outside the use of this tool by the registered account. You control this data and can remove it from within your account at any time.
What information is stored locally? i.e. Cookies
Browser cookies are used for accessing your User Account and to store certain user interface settings such as when you have seen the side tips and want them hidden. We do not use them for anything else.
Calculations
The calculations are done client side, this means that they are not stored anywhere online but are generated by your computer each time you access the page.
All the objects and settings are saved in the URL.
Images
Images are referenced by their URL or filename.
It is important that you do not reference images that breach license, copyright or legal restrictions and that you understand that the model will no longer have access to the image if it is removed.
They are not automatically stored on our servers and are only temporarily cached on your computer when generating the model.
Upload Image
Local image files can be uploaded to your User Account to become accessible to others when you share the URL. Subscription only
Getting help
This tool is made freely available for you to use but unfortunately we cannot offer free technical support if you get stuck.
Please sign up to our subscription service to access technical support.
We are keen to hear feedback. Please contact us using the online form.
References
Calculations
- ISO 9613-1:1993 — Attenuation of sound during propagation outdoors — Part 1: Calculation of the absorption of sound by the atmosphere
- ISO 9613-2:1996 — Attenuation of sound during propagation outdoors — Part 2: General method of calculation
- ISO/TR 17534-3:2015 — Acoustics — Software for the calculation of sound outdoors — Part 3: Recommendations for quality assured implementation of ISO 9613-2 in software according to ISO 17534-1.
Quality Assurance and Test Cases: https://dbmap.net/iso17534results
Sound power levels
- BS 5228-1:2009+A1:2014 — Code of practice for noise and vibration control on construction and open sites.
Permission to reproduce extracts from British Standards is granted by BSI Standards Limited (BSI). No other use of this material is permitted. British Standards can be obtained in PDF or hard copy formats from the BSI online shop: www.bsigroup.com/Shop
Colour scheme
Javascript Libraries
- JQuery (Programming)
- SnapSVG (Object drawing)
- THREEjs (3D View)
- Delaunator (Topography triangulation)
- MarchingSquares.js (Contour calculation)
- DXF-Parser (Object import)
- LZ-string (URL compression)
- jsPDF (PDF output)
Calculate Grid
How to add a point source
- Tap/Click anywhere to insert a point source
What is a point source?
This is a source of noise that radiates from a single point and in all directions in a spherical shape.
Using the select tool
- Click on a source once to disable it
- Touch/Click and drag to move it around.
How to add a line source
- Touch/Click and drag to draw a single line section
- Tap/Click successively to draw a line source with multiple sections.
- Right click or Double click to end the line.
What is a line source?
A line source radiates sound in a cylindrical shape from the line sections and in a spherical shape at each end.
Using the select tool
- Single Click on the middle of a line source to disable it.
- Touch/Click and drag to move it around.
How to add a barrier
- Touch/Click and drag to draw a single barrier
- Tap/Click successively to draw a barrier with multiple sections.
- Right click or Double click to end the barrier.
- Alternatively Tap/ Click the start point to make it a building.
What is a barrier?
This is a screen that both breaks sound paths and potentially reflects them, such as walls and solid fences.
It is not currently possible to model floating barriers or ceilings.
Using the select tool
- Single Click on the middle of a barrier to disable it.
- Touch/Click and drag to move it around.
How to add a building
- Touch/Click and drag to draw the dimensions of a four sided building
- Use Shift to keep it at right angles
To draw buildings with more than four sides, use the Add Barrier tool.
What is special about buildings?
These are the same as barriers except that internal walls are ignored and the area within is not calculated.
Sloping roofs can be added to any buildings with four parallel sides. All other buildings have roofs that are flat and perfectly horizontal.
Reflections are not considered from the roof surface.
The building height is relative to the ground height at the first point. More information can be found in the guide
How to add a receiver
- Single Tap/Click anywhere to insert a decibel level receiver
What is a receiver?
This is a marker where the total decibel noise level is calculated at the specified height along with an optional frequency spectrum graph.
Using the select tool
- Click on a receiver to toggle the frequency graph display
- Touch/Click and drag to move it around.
How to add a ray-receiver
- Single Tap/Click to insert a ray-receiver
What is a ray-receiver?
All sources of noise will have lines drawn directly to these receivers to indicate sound propagation paths or "rays".
When showing waves, the wavelength is drawn to scale.
When showing lines the dashes represent different frequency bands.
Using the select tool
- Click on a ray-receiver to disable it
- Touch/Click and drag to move it around.
How to add an accessory line
- Touch/Click and drag to draw a single line
- Tap/Click successively to draw a line with multiple sections.
- Right click or Double click to end the line.
What is an accessory line?
These lines can be used for measuring distances or simply for illustration.
You can also convert between accessory lines and other objects.
Using the select tool
- Click on the middle of a line to toggle measurement.
- Touch/Click and drag to move it around.
How to add an image or map
- Tap/Click to insert an image file or Google Map.
- Drag and drop image files into the browser window.
Using the select tool
- Maps will be inserted to scale. Touch/Click and drag to reposition.
- Images will need to be resized. Use the "Calculate Scale" option or the handles for resizing and rotating:
When rotating, hold the Shift key to constrain to right angles
Add a ground height point
- Tap/Click anywhere to insert a height point
What is a ground height point?
This defines the ground height at a point and is used for triangulating ground topography and creating slopes.
Add a ground height line
- Touch/Click and drag to draw a single line
- Tap/Click successively to draw a line with multiple sections.
- Right click or Double click to end the line.
What is a ground height line?
This defines the ground height along the line and is used for triangulating ground topography and creating slopes.