Presenting the impact of aircraft noise

Opendate_range11 Nov, 2021, 12:01am - 28 Feb, 2022, 11:59pm

Presenting the impact of aircraft noise

Noise contours

To view a map of noise contours relating to this consultation please click here 

Noise contours are lines on a map that connect points of the same levels of noise exposure. Contours are a standardised industry method of presenting the average aircraft related noise experienced (or projected to be experienced) by people living around an airport. They were traditionally calculated over a 16-hour period (07:00 – 23:00) during the busiest 92-day airport summer period from 16th June to 15th September. Contours may be calculated (to present information on what occurred in the past) or modelled (presenting information for expected future conditions).

The use of average noise contours facilitates: -

  • an examination of noise exposure trends over time;

  • a comparison of different operating scenarios;

  • an examination of the predicted impact of development proposals.

We understand that a lot of technical terms are used in relation to aircraft noise. We try to present information in a format that is easy to understand but where the use of technical terms is unavoidable, we will explain why we have used them and what they mean.

Metrics used to present the effects of aircraft noise in this consultation

Why we have used the metrics Lnight and Lden to present the impact of aircraft noise at Dublin Airport

The European Communities (Environmental Noise) Regulations 2018 (ENR) prescribes a common method for noise mapping to standardise noisemapping assessments and make it easier to compare data across countries. These include the night metric (Lnight) and the day-evening-night metric (Lden).

Other metrics referred to in this consultation

Many historical planning conditions relating to Dublin Airport (those relating to insulation schemes for example), relate to the 92-day day-evening summer period metric (LAeq16). Legislation permits the use of additional metrics such as this where they are relevant to local circumstances.

insert_chart What these metrics mean

Lden

(day-evening-night noise level in dB):

the long-term average indicator in decibels, designed to assess annoyance and defined by the ENR. It refers to an A-weighted average sound pressure level over all days, evenings and nights in a year, with an evening weighting of 5 dB and a night weighting of 10 dB.

Lnight

(night noise level in dB):

the long-term average indicator in decibels, designed to assess sleep disturbance. It refers to an A-weighted annual average night period of exposure.

LAeq.16

(day-evening noise level in dB)

the long-term average day-evening (07:00-29:00) indicator in decibels, for the day-evening period during the 92-day busy summer period from 16th June to 15th September. It refers to an A-weighted average noise exposure over this period. This metric in isolation, does not capture night-time noise and is often used in conjunction with an 8-hour night-time metric that is averaged over the same 92 day period (e.g. LAeq.8).

A-weighting

Noise can be measured and evaluated objectively but humans have a different response to different frequencies. A-weighting is an industry agreed adjustment that is made to sound measurements to replicate the response of a human ear. It is generally represented as dB(A).

The periods of a day are defined in legislation as:

Day is 07:00-19:00, Evening is 19:00-23:00; Night is 23:00-07:00.