Other Important Issues

Noise

This is probably the environmental issue that will be of most concern to local residents.

Parts of the surrounding area are already subject to back-ground noise from road traffic and railway trains. This is not taken into account in these noise patterns, which are just about aircraft, modelled in a consistent manner using The Integrated Noise Model (INM) developed by the US Federal Aviation Administration (FAA) using the inbuilt aircraft types and noise characteristics. (Note: measure-ment of actual aircraft noise characteristics and track-keeping may result in lower noise levels).

Existing Noise Pattern

The following drawing shows the existing noise pattern generated using the FAA INM noise model. This reflects 75,000 annual movements that are primarily general aviation. The model assumes existing runways and usage and existing routes and circuit patterns, but is "idealised" in that it does not allow for variation in flight track keeping.

OPTION A Existing Runways With Increased Runway Movements

"Reproduced from the 1999 OS Ordnance Survey 1:25,000 scale map with the permission of the controller of HMSO
License Nr: AL 100019901"

The above shows the predicted noise pattern generated using the same INM model, but with primarily general aviation movements increased to 100,000 annual atms. The model again assumes existing runways and usage and existing routes and circuit patterns.

OPTION B New Runway With Increased Runway Movements

"Reproduced from the 1999 OS Ordnance Survey 1:25,000 scale map with the permission of the controller of HMSO
License Nr: AL 100019901"

The above shows the predicted noise pattern generated using an same INM model with 75,000 general aviation movements plus 25,000 commercial movements. The model assumes most aircraft use the replacement 05/23 runway alignment and appropriately modified circuit patterns.

Noise Contour Values

For our INM study we have used the LAeq unit of measurement. This is a widely accepted measure of noise, weighted for factors such as time of day, or the number of movements.

Research shows that below an exposure level of 57 LAeq the percentage of affected individuals who are highly annoyed by aircraft noise is very low. This value is therefore seen as the threshold, above which the population surrounding an airport is considered as being "affected" by aircraft noise. It is recognised that such a measure is fairly subjective, as an individual can still be annoyed by noise levels below this figure, but this is a recognised standard for community response.

The LAeq values are quoted in decibels (db), which is a logarithmic scale of energy levels that can be confusing.

A 3db change is the minimum change that can be distinguished by humans.

A 10db increase is perceived as being twice as loud.

Previous page    Next page