• Lday is the A-weighted long-term average sound level for the daytime period (07.00 to 19.00).
• Levening is the A-weighted long-term average sound for the daytime period (19.00 to 23.00).
• Lnight is the A-weighted long-term average sound level for the daytime period (23.00 to 07.00).
• Lden – is the A-weighted long-term average sound level for the day-evening-night noise indicator in decibels (24 hours).
The European Directive 2002/49/EC on noise mapping requires noise contours to be generated using the Lden and Lnight noise indices. The Lden unit is a LAeq for the whole 24 hour period but includes weightings depending on when during the 24 hour period the noise occurs.
LAeq.T is the most widely applicable unit and is the equivalent continuous A-weighted sound pressure Level. LAeq.T is an energy average and is defined as the level of a notional sound which, over a defined period of time, would deliver the same A-weighted sound energy as the actual fluctuating sound.
If the noise is during the 12 hour day (07:00 – 19:00) there is no adjustment. If it occurs during the evening (19:00-23:00) a weighting of +5 dB(A) is added and if it is at night (23:00 – 07:00) a weighting of +10 dB(A) is added. The unit is therefore biased to respond more to noise in the evening, and particularly at night, than during the 12 hour day.
In movement terms the effect of the weightings is equivalent to more than trebling the number of aircraft movements during the evening and multiplying by 10 the number of movements at night.
To compute the noise contours each period is considered separately and a LAeq is determined for it. The weightings are then added to the evening LAeq and night LAeq with each LAeq then added together, taking into account the period durations.
*Please Note: The date 'October 2012' indicated within the contour maps below is the Map publication date only. The contour maps refer to the calendar year 2011.
2011 Dublin Airport Lden Oct
2011 Dublin Airport Lnight Oct
Web Design & Development by Arekibo