EU Directive 2002/49/EC, transposed into Irish law by Statutory Instrument number 140 of 2006 (the ‘Environmental Noise Regulations 2006'), calls for the development of strategic noise maps and action plans for major roads, railways, airports and cities.
Under the Regulations, TII is responsible for the development of noise maps for all national roads carrying in excess of 3 million vehicles a year.
For the 2012 phase of noise mapping, strategic noise maps were developed for just over 3000 km of national roads. Additional noise maps were also developed for major non-national roads. The website displays noise maps for major roads outside the agglomerations of Dublin and Cork. These maps were developed by the Authority in 2012.
What is a Noise Map?
A noise map is a graphical representation of the predicted situation with regards to noise in a particular area with different colours representing different noise levels in decibels [dB(A)].
To develop a noise map a number of variables must be determined in order to correctly represent the amount of noise generated at the source, i.e. by traffic driving on the road. The noise level at the source is primarily influenced by the speed at which traffic is travelling at, the overall quantity of vehicles in the traffic flow, the proportion of heavy commercial vehicles (HCVs) in the flow and the type of road surface in the area.
The manner in which the noise propagates away from the source must then be calculated which involves determining the reduction in noise level as it propagates from the source. Distance, ground cover and the presence of barriers such as walls, noise barriers, etc. will all influence the level of noise attenuation.
Lden is the day-evening-night noise indicator and it represents the noise indicator for overall annoyance. It is ‘weighted’ to account for extra annoyance in the evening and night periods.
These indicators are based on year long averages of the day (07:00-19:00), evening (19:00-23:00) and night (23:00-07:00) time periods.
National Strategic Noise Maps
Strategic Noise Mapping 2012 Lden Web Map
Lden is the calculated day-evening-night noise level and represents the noise indicator for overall annoyance. It is calculated over all day-evening-night periods for one year. The day period is from 07:00 to 19:00, the evening period is from 19:00 to 23:00 and the night period is from 23:00 to 07:00. The Lden indicator contains extra weighting for the evening and night periods as noise is generally more annoying during these periods. The map below indicates the Lden decibel (dB) bands reported for Strategic Noise Mapping 2012.
Strategic Noise Mapping 2012 Lnight Web Map
Lnight is the night time noise indicator and is used in the assessment of sleep disturbance. It is the average noise level calculated over all night periods, 23:00 to 07:00, for one year. The map below indicates the Lnight decibel (dB) bands reported for Strategic Noise Mapping 2012.