Extract from the British Model Flying Association (BMFA) Hand book in the UK.

METHOD OF MEASUREMENT OF NOISE
EMITTED BY A MODEL AIRCRAFT
The model, working at maximum rpm, should be
held between 1 and 2 metres off the ground in a
bracket or by one person standing upwind of the
model. The microphone of the noise meter should,
where necessary, be fitted with a windshield. It
should be positioned downwind of the model, 7
metres away from it (measured horizontally), and
1.2 metres vertically from the ground. The wind
speed should not be over 3 metres per second
(force 2).
Measurements should be taken in the open air and
away from reflecting surfaces such as buildings.
The noise level emitted, for the purposes of this
Code, shall be the maximum value of four readings:
(I) model pointing directly at the meter,
(ii) model pointing directly away from the meter,
(iii) model pointing 90o to left of meter,
(iv) model pointing 90o to right of meter.
The noise meter shall be in accordance with
BS5969:1980 (‘Specification of sound-level
meters’), using the A-weighing response, and with
the meter set to ‘slow' response. The meter should
be calibrated prior to use.

Hope this helps.

MIke