A noise map is rather like a weather map: it shows the hotspots where it is noisy and the cooler areas where it is quiet. Noise maps are produced by computer software which predicts the noise level at a specific point as it spreads out from the sources of noise that have been included. The software takes account of features which affect the spread of noise such as buildings, the shape of the ground and whether the ground is acoustically absorbent (e.g. a field) or reflective (e.g. concrete or water).
Noise maps have three main purposes:
- They can be used to find areas where noise levels are high and these can be linked to population data to estimate how many people are affected
- They can help in the production of noise action plans to manage noise and reduce noise levels where appropriate
- They can be used to test the effectiveness of different methods of reducing noise, whether by planning – e.g. re-routing traffic – or noise reduction techniques – e.g. noise barriers. Alternative approaches can be rated according to the number of people benefited and the cost of implementing the plan to decide which are the most cost-effective.
Noise maps can also help to identify quieter areas which can be protected.
Under EU Directive 2002/49/EC of 25 June 2002 relating to the assessment and management of environmental noise, noise mapping must be carried out for all agglomerations with more than 250,000 inhabitants and for all major roads which carry more than six million vehicles a year, as well as major railways which carry more than 60,000 trains per year and major airports.