Guidance

Military Aviation Noise Contours

Published 24 August 2022

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The Environmental Noise Regulations 2006 require the creation of strategic noise maps and the formation of noise action plans. The mapping of environmental noise levels generated from aviation activity at Royal Air Force stations is delivered by the Noise and Vibration Division (NVD), from the Royal Air Force Centre of Aviation Medicine (RAFCAM), in the form of Military Aviation Noise Contours (MANC’s).

Although the Environmental Noise Regulations 2006 do not apply to military activity, to ensure the Royal Air Force’s approach remains ‘as good as that required by legislation’, the NVD RAFCAM conduct thorough documentary reviews of government papers, studies by the World Health Organisation and the Civil Aviation Authority. The NVD also consult industry experts, both in the UK and the USA to ensure a robust review of current practices within the industry.

The environmental noise contours produced by the NVD RAFCAM depict the noise levels created by the aviation activity at a given station within a given time domain. Computerised environmental noise levels are calculated by taking the noise characteristics from a given aircraft[footnote 1] and the expected flight trajectory[footnote 2] to determine the propagation of the noise to ground level.

The computational noise software used by the NVD RAFCAM to undertake environmental MANC modelling is the Federal Aviation Administration, Aviation Environmental Design Tool (AEDT). The AEDT models an aircraft performance in space and time to quantify the environmental noise produced at a given location. The AEDT supersedes the Integrated Noise Model previously used to produce military noise contours.

Environmental noise contours graphically show the noise emitted from aviation activity surrounding the airfield. The noise is represented as contour bands depicting different boundaries of noise levels. The contour seen closest to the runway shows the loudest noise, then typically decreasing with distance for each contour. There are some exceptions to this generalisation, for example when heavy circuit work is conducted at a station. If heavy circuit work is conducted, then the noise levels around the circuit area will increase and this can be seen in the shape of the contours.

The measurement of sound is undertaken using the decibel (dB) scale. Sound level in decibels is measured and averaged over a stated time period. The human ear does not detect all frequencies of sound equally efficiently (the ear responds less to very high and very low pitch sounds). To compensate for this, electronic filtering is used[footnote 3] to mimic the varying sensitivity of the ear. The contour is typically further defined by the average level of noise produced by the activities throughout a 16-hour period[footnote 4] (known as LAeq), which is the characteristic utilised in international standards relevant to environmental noise assessment.

Noise contours use a form of time averaging, such as 16-hours (LAeq), 12-hours[footnote 5] (known as Lday), 4-hours[footnote 6] (known as Leve), 8-hours[footnote 7] (known as Lnight), and 24-hours[footnote 8] (known as Lden). These show the average noise level around an airfield during that specific time period, over an annualised representative flying day. The 24-hour Lden period is calculated using Lday, Leve and Lnight information however, to take into account the annoyance induced by noise during the sleeping and the evening periods, an additional dB penalty of 5dB is added for the evening period (usually from 19:00 to 23:00) and 10dB for the night period (usually from 23:00 to 7:00).

Additional information about specific Royal Air Force stations

Historical environmental noise contours

Note: The Noise Amelioration Scheme (Military) was withdrawn on 8 July 2021. Historical environmental noise contours are available for information purposes only.

  1. known as Noise, Power, Distance curves and associated spectral class ↩

  2. speed, altitude, and engine thrust request ↩

  3. known as A-weighting’ and signified as dB(A) ↩

  4. An energy equivalent noise metric utilised during the 16-hour period (07:00 to 23:00) ↩

  5. An energy equivalent noise metric utilised during the day period (07:00 to19:00) ↩

  6. An energy equivalent noise metric utilised during the evening period (19:00 to 23:00 ↩

  7. An energy equivalent noise metric utilised during the night period (23:00 to 07:00) ↩

  8. An energy equivalent noise metric utilised during the 24-hour period with an evening penalty of 5dB and night penalty of 10dB ↩

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