I am not justifying the noise lobby, but ....
over Crystal Palace, airliners are at idle thrust, descending through about 4500 feet. Not quite the same as approach thrust in the last four or five miles.
The Boeing website had very useful information on the environmental impact - <a href="http://www.boeing.com/commercial/value/quieter.html" target="_blank">here</a> is a link of interest, hopefully, although there were a series of leaflets they once produced which were excellent resources.