At my field, people often mention noise levels and their choice of a muffler to satisfy noise regulations (something about 92DB?).
However I have never seen anybody coming with a meter and checking noise levels of different planes at the field. Is it something I need to take into account - and how? I have an OS SF-61P waiting for me to grow up. I am planning on purchasing a MACS muffler for it. The SF supposedly is noisier than an FX, and this free-flow muffler will sure make it even noisier. The question is - is it still legal in AMA fields?

The noise regulations vary from field to field and to the best of my knowledge are not regulated by The AMA.

As far as your question goes I'd say its something to take up with the local club. You say the limit is 92db but usually for that type of measurement to be meaningfull there is also a distance measurement. Like 92db at 6 feet. I would strongly suggest getting all the information regarding noise limits at that particular field. Especially if they don't use a meter. Different pitch noises can acually be percieved as being louder and then they are.

The AMA doesn't have noise regulations.

They do have some suggestions posted, however.

Some forms of competition have very specific nose rules.

It's not uncommon for people to mistake either the AMA recommendations or a particular competition class noise rules for general AMA rules.

As Crashem noted, individual fields may have their own noise regulations.

My home field has no noise regulations because no one lives very close to us. I even fun an old OS .61FS (four stroke, pre-surpass line) open stack, no muffler at all. It doesn't sound loud because it's low frequency noise, but it's actually pretty noisy on the ground.

If you want to reduce noise on your plane, there are lots of things you can do, different mufflers, prop brands and sizes, airframe vibration noise, and more.

Balancing your prop will help too

The engine exhaust only accounts for some of the noise an RC engine makes. The prop also contributes. If you find that your .61 is too noisy then increase the prop size first. The may bring you into compliance. If not, you can perform some "modifications" to the muffler. Some modelers put steel wool in them to form a sort of baffle. This would probably work ok, but you'll lose some power.

The Mac's should do a decent job of muffling it despite your fears. If you are looking for max power at low decibels try a Davis muffler. They are supposed to be quite quiet and give a moderate boost in power.

Mark Shuman