GBR2

My Feedback: (1)

I know the AMA recommends a dB limit of 90dB at 3 meters but they have absolutely NO document on their website that explains how to do it and lists the limit. I know it is only a recommendation but shouldn't there be some document to support it?

Rodney

Try Google, there is a wealth of info on sound measurements and equipment required available. Also, most physics books will provide you with the basic knowledge to work it out yourself.

cj_rumley

There was a document compiled by Howard Crispin and published by AMA, "SOUND AND MODEL AERONAUTICS, A handbook for model clubs" 145 pp., 1991. It was still available in Jan '98, as I was sent a copy, as I suppose were others that contributed something to the Sound Committee. I don't know if it can still be obtained from AMA, though.
The recommended 90 dBA at 9 ft was changed slightly to a measurement distance of 3 meters circa 1999 by Steve Kaluf, then Tech Dir, mainly to get in step with most of the that uses metric units of measurement. AFAIK, it still applies to aerobatic competition rules, so you may find some useful guidance there.
As far as model clubs go, the recommended limits were changed when the Sound Committee, idled since passing of Crispen, regrouped. The reestablished committee saw the "one-size-fits-all model fields" fixed limit on sound source level as irreconcilable with received levels nearly universally specified by local noise abatement ordinances, and vary widely depending on factors including zoning, time-of-day, and the period over which measurements are averaged (few specify instantaneous measured levels, most set limits as average levels measured over one hour, at the property line). That remains the AMA advice (AFAIK) to this day: Find the allowed levels in local codes and ordinances established by the appropriate authority (usually city or county, never AMA) and abide by them. The committee did provide guidance on how to set club limits to meet the local standards for sound emissions, and also how to make model power plants meet the club standards. These were published in quarterly 'Sound Advice' columns in The AMA News section of MA. Rough recall is they ran from mid 1998 thru early 2000 when it was disbanded by then prexy Dave Brown. Usually the 1st article in that section, and with sufficient resolve you can find them in MA archives.......frankly, I don't have the patience to use that database, so you're on your own there.

aeajr

My Feedback: (2)

As far as I know, the only way to measure sound level dB is with a meter and the meter will have instructions.  AMA only has to tell you what the recommended limit would be.  You have to read the manual for your particular meter.

Membership Manual- Page 36
http://www.modelaircraft.org/files/memanual.pdf

Leader Club Electives:

1) Club has implemented and enforces a frequency-control plan

that allows all 50 RC channels to be used at its club flying site

where RC is allowed.

2) Club has implemented a school program or donates a

Aviation

3) Club conducts a review of the AMA Safety Code at a club

meeting at least once a year.

4) Club sponsors an annual public event, such as a mall show,

flying show, or demonstration.

5) Club monitors noise levels and/or institutes club field rules

such as a requirement that models be operated at a maximum of

90 db at 9 feet.

Modelmagazine subscription to schools or libraries.

TexasAirBoss

My Feedback: (22)

The AMA has established 14 goals for leader clubs. They may select any 5 of the 14.They need not be the 5 that youchoose.

andboy

My Feedback: (4)

I haven't checked, but is it 90dB or 90dB(A) @ 3m?

There is a difference, A weighting is now commonly used to simulate the sensitivity of the human ear.

I don't want to say it, but Radio Shack sell something they call a Sound Level meter, however, without calibration you don't know what it is measuring. In it's defense, I have used a calibrator and, at least the ones I have had the misfortune to come across, are fairly close to the 94dB at 1kHz. Without any other mfr info, you just don't know what it's doing at other freq's.

Measuring it on the ground, vs being held in the air, vs flying also have a great effect.

I probably haven't helped much, but I would imagine you measure with it on the ground, on axis, most likely with A weighting selected on a fast or impulse setting (if your equipment has that).

vicman

My Feedback: (10)

Just read your current issue of MA and your answer will come to you.

TexasAirBoss

My Feedback: (22)

Low frequency sound propagates the furtherest.

AMA rules state each aircraft must have a muffler, period. Any sound level limit must be adopted by each club individually.

IMAC aircraft are exempted from any club sound level rule.

IMAC aircraft make the type of sound that propagates the furtherest and they are exempt.

Unless yur club is restricted to "glow only", it is not possible to effectivelygovern thenoise made.

vicman

My Feedback: (10)

Read it again chief.

TexasAirBoss

My Feedback: (22)

I just read it. Care to gleam some light on your comment ?

Ishould add that I am reading from the website,

vicman

My Feedback: (10)

What about engines that didn't have mufflers OEM? IE Cox 1/2a.

TexasAirBoss

My Feedback: (22)

Tatone makes, ( or made)after market mufflers for Cox engines. The AMA rule doesn't appear to exempt them.

Let me add that I think this rule was made after the hayday of 1/2 A was past. I flew 1/2A in the late 70's and I never used a muffler and I don't think it was required at that time.

andboy

My Feedback: (4)

That is true as it has the most energy.

However, it is not the sole determining factor. The noise spectra plays a large part (the whining of a 2 stroke is at a higher frequency where the ear is more sensitive) as well as prop choice etc. etc.

The psychological aspect of large pieces of wood and metal flying above people, lead them to look for other more objective things, and complain about them.