Sound Propagation Level Calculator

How to use

• Choose between "Single Frequency" for tonal sources and "Multi-Spectrum" for broadband sources.
• Edit sound levels and distances (in metres) or click and drag the items in the diagram to modify their position.
• Move the barrier/building top to change its position, click the body to toggle on/off.
• Click "Wall+" to add a reflective surface behind the source/receiver.
• In "Single Frequency" mode click "Show calculation breakdown" to see the effect of the attenuation factors listed below.
• You can bookmark or link directly to the results by clicking "Link to this calculation" under Options.
• Need to calculate with multiple sources? Check out our other tools

This is an approximate calculation tool and should not replace your own calculations and real-life measurements.

Assumptions

• No significant sound transmission around the barrier sides. The total level around the sides of the barrier must be at least 10dB below that from over the top of the barrier.
• No significant sound transmission through the barrier. The total level through the barrier must be at least 10dB below that from over the top of the barrier.
• There are no reflections from the barrier. In reality when dealing with short distances and many reflective surfaces the "canyon effect" may occur with repeating reflections.
• There are minimal affecting weather conditions, such as wind or temperature inversion, as these will affect the propagation path of a noise source and diffraction around the barrier.
• The noise source behaves as a point source and is far-field, where inherent directivity is minimal.
• Walls used in the model are considered to be perfectly reflecting and at 1 metre distance (facade level).
• Conditions are free-field and there is no reverberant field.

Sound Attenuation due to Propagation ("Geometrical Divergence")

Sound waves propagate as a sphere and follow the "inverse square law" of level reduction.

A general rule is that the level reduces by 6dB per doubling of distance.

Sound Attenuation due to a Barrier using ISO9613-2:2024

Sound waves are reduced by a barrier depending upon the frequency of the sound waves with lower frequencies less affected. The greater the path difference, the more effective the barrier is.

A general rule is that a single barrier at eye level with a source and receiver will reduce the level by approx 5dB.

The barrier attenuation calculation in the guidance is limited to 20dB for a single barrier and 25dB for two barriers. Toggle this with the "Apply limit" checkbox.

Ground Effect (reflection and absorption) using ISO9613-2:2024

Sound waves are 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).

• 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.

Air Absorption using ISO9613-1:1993

As sound waves travel through the air a small portion of the energy is converted into heat depending upon the atmospheric temperature and humidity, however the amount is only significant with high frequencies and long distances.