Hello all
I thought that it would be interresting to get som ideas of how people are able to pass the sound-measurement (without cheating !) when using the newest and most powerful engines. This year I have been flying mostly with batteries, but I have played around a little bit with the OS FS-200S FI. Last year when I flew with the OS 140RX-FI and 18x10 prop I measured very close to the 94db limit. The OS 200FI spins the same prop at around 1000 RPMS more, no way that can pass the test. We did measure it with 17x12 over grass, and it was close to 94db' there (limit is 92 on grass). The YS160DZ powered Genesis of a friend of mine, spinning the same 18x10 was measured to more than 98db (that is more than twice the energy than the 94db limit)!

The question is really this ; How do you do it, here is a couple of alternatives :

1 : Cheating with less servo travel during noise test
2 : Never measured, and i do not bother
3 : Struggling by running a small diameter high pitch prop that makes the model hard to keep at slow nice speed.
4 : Three (or more) bladed prop of type X, size Y
5 : Are not using the short mufflers from Hatory, they are too noisy
6 : Another new and brilliant solution

I'm really looking forward to get som valuable inputs on this one !

Regards
Ola Fremming