Hi all,

this post really is most applicable here in the UK where space is at a premium so that many flying sites have noise sensitive neighbours quite close by.

However, I am sure that the expertise is here to solve my problem!

The DoE (department of environment) here in the UK has a noise limit for model planes of 82dB(a) at 7m measured over graass. This is what we need to work towards at our regular flying clubs to maximise our "legitimacy" in the event of a noise complaint. However, this works out at quite a bit below the FAI limit of 92dB(a) over grass at 3m.

I am struggling to get my Alliance through the 82dB test as although it "sounds" quiet in the air it is testing out as quite noisy.

The model has the following setup:

YS 140DZ
Hyde mount
16x12 prop at about 8500rpm
Hatori manifold
Hatori 698 pipe soft mounted.

This is all fairly standard stuff and it does pass the FAI limit for being legal to compete with. However, it there anything I can do to reduce the noise further without compromising the performance?

For instance, has anyone tried an air filter type arrangement on the carb intake? Does it make much difference to the noise and would it have much effect on performance?

Would a different header be any quieter? Or would an additional add-on muffler on the end of the exhaust affect the noise or power?

Any thoughts and suggestions will be gratefully received.

thanks in anticipation,

James