The article on May 11, 2009, by Brian Iler alludes to the method of calculation of acceptable aircraft noise, however he does not elaborate.

The Tripartite Agreement is very clear in stipulating that procedures for calculating “excessive” noise are set out in ICAO (International Civil Aviation Organization) Annex 16, Chapter 5 and Appendix 2 for aircraft such as the Q400.

ICAO stipulates limits for three noise levels, namely takeoff (flyover); sideline at takeoff; and, approach. It also indicates that two of the three levels may be exceeded, although not more than 2.0 decibels each, and the total of the two not to exceed 3.0 decibels. The caveat, however, is that the total number of decibels that are exceeded in those measurements must be offset by the third parameter. That is, the third parameter must be below the decibel limit by a sufficient margin to offset the other two measurement parameters.

The Q400 aircraft, which is utilized by a commercial carrier at the Toronto City Centre Airport, has a takeoff (flyover) value of 78.0 and the limit is 84.0; i.e. 6.0 decibels under the limit. In summary, no restriction is exceeded by more than 2.0 decibels [the maximum exceeded parameter is 1.1 decibel over the limit]. The accumulation of exceeded decibel values is 1.6 [well below 3.0] and the offset is 6.0 decibels for a total reduction of 4.4 decibels pertaining to an “aircraft generating excessive noise”.

Further data on the Q400’s noise rating and the TCCA Noise Management Study currently underway can be found at http://www.torontoport.com/airport_NMprogram_b.asp

Ken Lundy
(Mr. Lundy is the Director of the Toronto City Centre Airport and an employee of the Toronto Port Authority.)