BLACKRIDGE & DISTRICT MODEL FLYING CLUB
METHOD OF MEASUREMENT OF NOISE EMITTED BY A MODEL AIRCRAFT
This procedure is specific to the Blackridge & District Model Flying Club but is based largely on the method of testing documented by the BMFA.
All noise tests should be carried out by 2 Club examiners.
The Club noise test table should be used at all times to ensure consistency of results
Noise test paperwork required is
A) Numbered noise test certificate
B) Noise test pass sticker
both should be completed during the noise test and the certificate returned to Club database keeper. The pass test sticker goes to the Member who must ensure it can be produced when the model is operating at the Club site.
Models submitted for noise testing must be fully assembled in flying condition.
Models failing a noise test must be resubmitted for testing if any of the specified items documented on the test certificate is changed.
No 'discretion' on actual noise meter readings should be used by examiners to ensure fairness and consistency.
Members should be allowed to make minor adjustments to the model during testing if items are contributing to noisy emmissions eg tightening a loose wheel which vibrates and causes noise.
Owners of models being tested should be encouraged to have a helper hold the model so they can see at first hand the meter readings during the test.
The model, working at maximum rpm, should be positioned and secured on the Club noise test table 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).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.
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.
Any of the above readings measuring greater than 80dB will result in a test fail for the model.
BMFA ADVICE ON THE NOISE TEST
The noise testing procedure noted in the DoE noise code above should be followed carefully but to get the best results it is strongly recommended that you should take special note of the following:
Make sure that no noise reflecting surfaces are near the test site. This means not just buildings but cars, concrete, models, model boxes and even hard packed earth. Do the test over grass.
Do not take measurements when there is any appreciable background noise. Traffic on a nearby road, other models flying or being readied for flight and even people talking near the meter can affect the readings.
Wind blowing across the microphone has a big effect on readings. Do not test on breezy days and when you do test, use a microphone wind shield.
Make sure that the actual microphone is over the end of the seven metre tape, not your hand or the centre of the meter.
Think carefully about the four test positions of the model at the other end of the tape. As a suggestion, for the sideways-on readings put the fuselage on the seven metre mark, for the nose-on reading put the propeller over the mark and for the tail-on reading line the trailing edge of the wing up with it.