Information on Noise Exposure
Transport noise affects about 900,000 people in Hong Kong. Unlike noise from industrial, commercial, construction and neighbourhood activities, it cannot be controlled effectively through the Noise Control Ordinance. Good planning is the better option and the Environmental Protection Department has intervened in the planning of new residential developments. Despite the constraints of massive road networks, about 90 per cent of new dwellings have been protected from traffic noise above 70dB(A) L10(1 hour).(1)
The airport was relocated from Kai Tak to Chek Lap Kok in 1998, giving relief to 380 000 people who had been exposed to severe aircraft noise. For the new airport, tighter noise standards have been adopted. According to the EIA in 1991 and the EIA update in 1998, only a very few of residents in North Lantau (about two hundred people) were within the NEF 25 contour of the new airport.(2)
To further reduce aircraft noise, a number of mitigating measures have been adopted. These include a preferential flight path during sensitive hours, the use of noise abatement procedures during take-off and the use of the continuous descend approach during landing. A sophisticated computer-based aircraft noise and flight track monitoring system, with 16 fixed noise monitoring terminals, has been set up by the Civil Aviation Department to monitor aircraft noise at different locations in Hong Kong.
||L10 (1 hour) is the noise level exceeded for 10% of the 1 hour period. It is generally used to describe traffic noise during the hour of peak traffic flow.
||NEF or Noise Exposure Forecast is an aircraft noise descriptor. It is a complex composite measure of exposure to aircraft noise, which takes into account the maximum flyover noise level, the duration and tonal characteristics of the flyover and the number of aircraft movements in both the daytime and night-time period. Details of information and noise levels at Noise Monitoring Terminals can be found in the website of the Civil Aviation Department at http://www.info.gov.hk/cad/".