Noise Mapping in Lille

Lille, with a population of 1091 million inhabitants is the 4th largest agglomeration in France after Paris, Lyon, and Marseille. Situated at the heart of a network of 464 km motorways connecting six European cities (Brussels, Bonn, the Hague, London, Luxembourg and Paris), the metropolis of Lille also has the densest railway network of France after Paris.

Pascal Thomas and his team of 8 people are in charge of collecting and analyzing data from traffic, parking, and noise in the urban community of Lille. They aim at obtaining a global diagnosis of traffic conditions and noise annoyance at different noise “hot spots” and to fulfill the EU Environmental Noise Directive 2002/49/EC.

To deal with the hot spots, the team use:

- 24 units 2250 Hand-held Analyzer with frequency analysis and basic logging. The plan is to use up to 70 units.
- Environmental noise calculation software Lima Type 7812 C
- Traffic counters:
* Radar-based, mounted on lamp posts
* Electromagnetic transducers mounted directly on the road surface on each lane

The traffic counters collect 15-minute average values of traffic flow, heavy vehicles and speed. These are used as input data for Lima™. The hand-held analyzers deliver 15-minute LAeq and spectra that are used to check the calculation of the existing situation in Lima in the following way:

1. Traffic flow and speed is surveyed simultaneously with acoustic measurements at different locations.
2. The geometry of the area is entered in Lima.
3. Input parameters (traffic, road surface) are entered in Lima.
4. Lima simulates the existing situation in 3D for day and night periods.
5. Calculated results are compared to measurement data.
6. If needed, input parameters for the calculation are manually adjusted to match the measurements.

Once the existing situation is correctly modelled, different scenario can be simulated to see if noise levels are reduced and conform with regulations.

This global approach gives a precise picture of the existing situation. Comparison with different predicted situations is a powerful tool to help decision makers choose the optimised solution. Pascal Thomas says “Brüel & Kjær was of great help to achieve these surveys because they delivered the right system and gave efficient training for advanced use of Lima”.

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