Defra has published strategic noise map data for England that give a snapshot of the estimated noise from road and rail sources across England in 2021. The data was developed as part of implementing the Environmental Noise (England) Regulations 2006, and is intended to help transport authorities to better identify and prioritise relevant local action on noise. It will also be useful for planners, academics and others working to assess noise and its impacts. An accompanying document explains the noise maps as being made using a new geospatial noise model developed by Defra. No actual noise measurements were taken in the production of the strategic maps, as the regulations require mapping to be carried out by means of modelling according to a specific method. This is because sound levels can vary significantly based on factors including weather conditions or the time of day or year, introducing a level of uncertainty into the result. This is averaged out as part of the modelling process. As a result, mapping data - although useful in helping authorities to identify priority areas for investigation - does not necessarily represent an exact picture of the current situation on the ground at any given locality on any given day.
https://www.gov.uk/government/publications/strategic-noise-mapping-2022/explaining-the-2022-noise-maps
