IMAC Sound Limits
 

Reading the IMAC Flying and Judging Guide, I see a section regarding Sound Limits. Is this sound test performed at every IMAC event? Is there a standard meter used for taking the sound measurements?

Thanks,

RE: IMAC Sound Limits
 

The sound scored is a judged item. Each judge enters it as
he scores your round. In my limited experience, if you are
really loud you get a zero, if you are pretty good, you get a
five and if you are really quiet (read canisters), you get
a ten.
Bruce

RE: IMAC Sound Limits
 

The section of the judging guide that I was trying to refer to discusses a sound test using a meter a specific distance from the plane (25'). Here is a small blurb from the manual:

Section 5.3:
"Prior to flying the first round of a contest; each competition model must pass the Ground Sound Level Test. The Ground Sound Level Test must be completed at the sanctioned contest site by the Contest Director or his/her designee."

RE: IMAC Sound Limits
 

They were big on sound testing at most contests the 1st year, not so much last year. It's up to the CD whether they sound test on the ground. You can always pass the sound test by reducing the ATV on the throttle. Then after you pass the test, increase your ATV and fly. You will still be judged in the air for loudness, but the score is very subjective. There is very little relationship of ground sound tests and perceived sound while flying.

What engine, muffler and prop are you planning to run? Folks can guestimate your sound score.

RE: IMAC Sound Limits
 

well heck, this one is new for me :) what can I expect with an OS 1.60 and a bisson pitts muffler? The engine (I think) is on the overpowered side for my 1/4 260, so I doubt I will ever be at full throttle for very long.

RE: IMAC Sound Limits
 

RichD,

You will be WAY under the sound limit. No worries.

Ken

RE: IMAC Sound Limits
 

Matt I assume you are putting a DA 150 into the Carden 260? ;) If so the MTW cans will probably drop right in. That with the right prop and it will pass when there is a ground sound check and get you 10's in the air. (of course a little throttle management will help in the air score)

Rob

RE: IMAC Sound Limits
 

Rob,

For the Carden 260, I will have KS Tuned pipes with a three bladed prop, so I am confident that bird will meet the sound limits :).

I also have a 2.6 Composite Arf Extra which will run a three bladed prop and slimline mufflers. This plane should meet the sound test with the three bladed prop, atleast I hope it will.

I was just surprised to see the actual ground sound test in the judging guide. The wording in the judging guide gave me the impression the sound test was required but I was getting the impression they were rarely done ;)

RE: IMAC Sound Limits
 

Yes but does anybody know the actual # of DBs in the rules.

RE: IMAC Sound Limits
 

5. Scale Aerobatic Sound Limits

5.1. Maximum Sound Levels

The maximum ground sound level for all classes shall be: 96dBA
measured on soft surfaces and 98dBA measured on hard surfaces.
Contest Directors may implement a correction factor due to unusual
conditions.

5.2. Standard Method of Sound Measurement

The sound measurement shall be taken with the sound meter set to the
“A” weighting, slow response with windscreen installed. The sound
meter shall be placed downwind, twenty-five feet from the model
centerline and positioned in line with the prop arc at twenty-four
inches in height (see Fig. 1). The sound meter shall be pointed di-
rectly at the model and perpendicular to the fuselage. The model being
measured shall have its engine run at full power for the sound test.
No noise reflecting objects will be allowed within three feet of the
sound meter.

5.3. Ground Sound Level Test

Prior to flying the first round of a contest; each competition model
must pass the Ground Sound Level Test. The Ground Sound Level
Test must be completed at the sanctioned contest site by the Contest
Director or his/her designee. Testing shall be done in an area designated
by the Contest Director and may be completed prior to or during
the first round. Models successfully completing the test will not be
measured again during the contest unless their sound level is deemed
to have increased significantly since the initial check by the Contest
Director. Any plane that fails the test will not fly, but will be moved
to the back of the flight order, and allowed one more attempt to pass
the test. Any model that fails the second test will zero all judged sequences
he would have flown during the current round. Any model
that fails the second test may be tested again during future rounds
with the same Ground Level Sound Test criteria being applied. No
model will fly any judged sequences at any Scale Aerobatics contest
until it passes the Ground Sound Level Test.

5.4. In-Flight Judging Criteria, Known and Unknown Sequences

Judges will evaluate each individual sequence flown in its entirety for
overall sound presentation. Each judged Known and Unknown sequence,
shall have one “figure” added to the end of the score sheet
after individually judged maneuvers. This figure shall be known as
the Sound Score. The Sound Score will have a K value dependent on
the class flown. Individual class K values shall be: Unlimited 5 K,
Advanced 4K, Intermediate 3K, Sportsman 2K, and Basic, 1K. The
bottom of each score sheet shall contain three boxes, Too Noisy, Acceptable
and Very Quiet. Judges will mark one of the boxes for each
sequence flown. These boxes shall translate in the computer to a
score of: Too Noisy - 0, Acceptable – 5, Very Quiet - 10. This score
will then be multiplied by the K value for the individual class. If two
judges are utilized, both judges’ scores must concur to issue a Too
Noisy penalty or a Very Quiet bonus. In absence of a Too Noisy or
Very Quiet” concurrence, an Acceptable will be scored for each sequence
flown. If three or more judges are utilized, a simple majority
concurrence will issue a Too Noisy penalty or Very Quiet bonus. All
Pilots that receive a Too Noisy penalty shall be notified of the penalty
by the Contest Director prior to the next round. Pilots that receive a
Too Noisy penalty will be allowed to adjust the aircraft setup and fly
the next round (Known Unknown). Any pilot, who receives a second
Too Noisy penalty during any Known, or Unknown, will be disqualified
from further competition at that contest.


Edited to format, copying from .pdf is... lacking