How do you measure sound form your engine?
09-04-2005, 10:43 PM
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How do you measure sound form your engine?
I have just got a DB meter from Radio Shack,
what is the procedure to measure the sound for my engine?
e.g. how far I have to be, what direction, e.t.c. what lenght e.t.c.
One of the old guys at our club says its too loud, but has no solid number to go by. It is supposed to under 98 db, but I don't know.
The engine is an evolution 35 cc with wrap-around pitts muffler.
what is the procedure to measure the sound for my engine?
e.g. how far I have to be, what direction, e.t.c. what lenght e.t.c.
One of the old guys at our club says its too loud, but has no solid number to go by. It is supposed to under 98 db, but I don't know.
The engine is an evolution 35 cc with wrap-around pitts muffler.
09-04-2005, 11:05 PM
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RE: How do you measure sound form your engine?
dB levels don't mean much unless you know at what distance from the source it was measured. Take measurements at 1 foot, 10 feet, 25 and 50 feet, with the engine at full throttle. To be meaningful when comparing the data to other engines, they must also be measured under the same conditions and criteria.
Noise level is also relative to the backgound, too. A 95dB @10 ft. noise is a lot more noticable at 5AM when there's nothing else happening than it is at 1100 in the morning with traffic sounds, dogs barking, lawnmowers running, a train in the distance, and a fire siren going down the road
Just so you have some 'ammunition' for when the neighbors complain about the noise, have somebody stand in the closest ones' driveway while you wind the engine up, and take a reading. If it's anywhere near or less than about 50 dB, they shouldn't have reason to complain. That's about the level of normal conversation. Anything above 65 or so starts getting annoying if it is continuous. (unless, of course, you happen to enjoy the sound of a gas or glow engine at full song
)
Noise level is also relative to the backgound, too. A 95dB @10 ft. noise is a lot more noticable at 5AM when there's nothing else happening than it is at 1100 in the morning with traffic sounds, dogs barking, lawnmowers running, a train in the distance, and a fire siren going down the road
Just so you have some 'ammunition' for when the neighbors complain about the noise, have somebody stand in the closest ones' driveway while you wind the engine up, and take a reading. If it's anywhere near or less than about 50 dB, they shouldn't have reason to complain. That's about the level of normal conversation. Anything above 65 or so starts getting annoying if it is continuous. (unless, of course, you happen to enjoy the sound of a gas or glow engine at full song
)
09-05-2005, 12:17 AM
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RE: How do you measure sound form your engine?
well how do most clubs generally do it?
I have heard the 98 @ 9' foot rule, 1 feet form above the ground perpendicular to the centerline of the fueslage of the plane
If I pass this test can I tell the old dude that is giving me a hard time to buzz off?[:-]
I have heard the 98 @ 9' foot rule, 1 feet form above the ground perpendicular to the centerline of the fueslage of the plane
If I pass this test can I tell the old dude that is giving me a hard time to buzz off?[:-]
09-05-2005, 10:14 AM
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RE: How do you measure sound form your engine?
Set the meter to the "human ear" scale. It's usually placed at the nose, at the engine level over grass, with the meter at 90 degrees to the sound source. In other words, the meter is 3' from the engine, facing it. Sound levels are usually what the club or controlling authority wants them to be.
Personally, unless someone objects, don't worry about it.
Dr.1
Personally, unless someone objects, don't worry about it.
Dr.1
09-05-2005, 11:21 AM
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RE: How do you measure sound form your engine?
well somone is objecting, he doesn't want me to fly...
so if I take a reading, 9 feet away from my plane and pass, I will tell the old dude too bad.
so if I take a reading, 9 feet away from my plane and pass, I will tell the old dude too bad.
09-05-2005, 02:25 PM
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RE: How do you measure sound form your engine?
In Europe, we take our readings at 7 meters (22 ft), and at a height of 1.2 meters (plane and meter) The plane is rotated through 8 positions, and the mean is taken. Meter setting A-weighted, slow. Many clubs take only one single reading, perpendicular to the plane at the exhaust side. The plane nose pointing into the wind. Typical limits are 80 dB(A) The same noise source will change by 3 dB when the distance is doubled or halved. (at 5.5 ft we would pass at 86 dB(A), at 3 ft that be ~89 dB)
The shorter distance used in the US make the measurements more prone to error, and very unreliable, so over here these are only valid at contests, for quick checks. Readings should be taken in calm weather, over grass. Due to noise reflections, Concrete runways add up to 3 dB to the reading, so be careful out there.
The shorter distance used in the US make the measurements more prone to error, and very unreliable, so over here these are only valid at contests, for quick checks. Readings should be taken in calm weather, over grass. Due to noise reflections, Concrete runways add up to 3 dB to the reading, so be careful out there.
09-05-2005, 02:27 PM
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RE: How do you measure sound form your engine?
The method used at my club is:
Over hard pavement
Meter is placed 10 ft. from the motor off of the right wing.
Meter should be held 1 ft. off the ground
Motor run up should last for 4 to 5 seconds.
Our club limit is 103 DB
I have a DA 50 with Slimline Pitts, Menz 22X8 that is 98 DB
DA 100 stock mufflers, MSC 26X10 that is 101 DB
There is another standard using 25 ft with lower DB reading however I am not familar enough with it to give you the specifics. Hope this helped.
Gary M
Over hard pavement
Meter is placed 10 ft. from the motor off of the right wing.
Meter should be held 1 ft. off the ground
Motor run up should last for 4 to 5 seconds.
Our club limit is 103 DB
I have a DA 50 with Slimline Pitts, Menz 22X8 that is 98 DB
DA 100 stock mufflers, MSC 26X10 that is 101 DB
There is another standard using 25 ft with lower DB reading however I am not familar enough with it to give you the specifics. Hope this helped.
Gary M
09-05-2005, 04:20 PM
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RE: How do you measure sound form your engine?
Here in Denmark most club limits are 94dB measured 3mtr (abt 10ft) perpendicular to the engine. So it would seem that you americans have all the luck...
But because of those rules, most "mufflers" bought from the US are completely worthless here.
Enjoy it while you can...
But because of those rules, most "mufflers" bought from the US are completely worthless here.Enjoy it while you can...
09-05-2005, 04:40 PM
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RE: How do you measure sound form your engine?
Here is the "official" IMAC standard.
IMAC Sound Rules
--------------------------------------------------------------------------------
Below are the IMAC rules with respect to sound. It is important to note that the rules in place will not change year to year. Further, it is emphasized that the maximum sound levels will not be lowered for 2004 and beyond from those listed below. Only a new rules making proposal during the normal AMA rules cycle, or a URP to the AMA would change the current sound rules. No action along these lines is currently contemplated or anticipated.
Wally Pitts
IMAC Sound Task Force Chairman
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.
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. The sound meter shall be pointed directly 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.
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.
IMAC Sound Rules
--------------------------------------------------------------------------------
Below are the IMAC rules with respect to sound. It is important to note that the rules in place will not change year to year. Further, it is emphasized that the maximum sound levels will not be lowered for 2004 and beyond from those listed below. Only a new rules making proposal during the normal AMA rules cycle, or a URP to the AMA would change the current sound rules. No action along these lines is currently contemplated or anticipated.
Wally Pitts
IMAC Sound Task Force Chairman
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.
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. The sound meter shall be pointed directly 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.
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.
