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MithraSIG provides three methods for calculating noise-impacted populations:

•The French method: NMPB 2008,

•The old CNOSSOS-EU method: CNOSSOS 2012,

•The new CNOSSOS-EU method: CNOSSOS 2020.

MithraSIG uses calculation receivers placed on building facades to determine the number of inhabitants exposed to each noise level interval. Each receiver represents one façade.

 

Methods

The NMPB 2008 method focuses on the most exposed façade of each building. It assigns the maximum noise level calculated to all the building's residents.

The CNOSSOS-EU 2012 method checks all building façades. It then assigns residents to each of these façades (dividing the residents according to the length of each façade in relation to the total length of the façades) and associates them with the noise level measured on that façade. In the case of individual dwellings (a single dwelling), it associates all the building's inhabitants with the level of the most exposed façade.

The CNOSSOS-EU 2020 method behaves in the same way as the CNOSSOS-EU 2012 method, except that it only takes into account half of the building's façades: the half most exposed façades. The residents are then distributed over these façades only.

Example: Collective building

To illustrate the differences between each method, let's take the case of a collective building measuring 24 m by 18 m, with 100 inhabitants. We've chosen to use an exaggeratedly large number of residents so that the differences can be clearly seen.

On this building, there is one large façade with high exposure, two façades with medium exposure and one façade with low exposure.

Here are the results obtained for each method:

Note: In the CNOSSOS 2020 and 2012 methods, the population is associated with the most exposed façade for individual dwellings.