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Volumic sources correspond to horizontal surface sources associated with one or more heights. In most cases, just one height is associated with the source.

Example of volumic sources:

- a football field (height of the source = 1m)

- a shipyard (height of the source = 5m)

These sources have an omni-directional directivity across the entire surface of the source. Their unit is dB(A)/m² (or dB/m² at the input of the spectrum). We're talking about "ground" power, so power per square meter of a horizontal surface. In case of multi-level source, power is distributed on each source height.

The number of sources on a single horizontal surface is limited to 500.

The spectrum (in m²) is distributed over each source based on the surface area and the number of vertical source. For a source, we have:

 num sources = num horizontal sources x num height sources

 Spectrum(Point source) = Spectrum(from User) +  10 x log10(polygon area) - 10 x log10(num sources)

Note: no source is created inside building.

 

Height of volumic sources

During a simulation, the origin z of the polygon of the volumic source is not taken into account. The polygon of the volumic source has its z equal to the z of the ground where it is situated during simulation.

However, the height of the sources point of the volumic source is important. The minimum height of a source corresponds to the half of the vertical distance between sources  (heightmin = 1/2 dist min between sources). Due to that, if we determine the vertical distance to 1m with 1 source, this one will be placed at 0.5m above the ground.

Height of volumic sources on buildings

For the case of volumic sources on buildings, the minimum height of the sources must be superior to the maximal height of the building, meaning Building height < 1/2 dist min between sources. Due to that, the first sources will be above the building.