Del Prado,
http://www.icao.int/publications/Documents/10031_en.pdf
ICAO Guidance on Environmental Assessment of Proposed Air Traffic Management Operational Changes
Table 3.1 seems to indicate that noise environmental impacts are relevant up to 10,000 feet and even, according to note 3 :
3. Noise may need to be assessed for changes above 10 000 ft (3 000 m)
in areas where the background noise levels are very low
(for example, in some specific areas protected by law), in
which case an upper limit of 18 000 ft (5 500 m), or higher, may be
more
appropriate in certain circumstance
In
Bracknell MP's rage at unannounced Heathrow flight path changes - Get Reading
the local rag says that "The staff told Dr Lee they were simply following procedure."
It would appear that the procedure isn't good enough and needs to be changed.