for Making Sound Level Measurements
Revision 0, December 02, 2003
Equipment: Radio Shack #33-2050 Sound Level
Meter (or equivalent)
Tripod to support sound level meter
Reference: AMA Radio Control Aerobatics,
Addendum 1 (Sound Addendum)
1. Place the airplane being checked on the ground, away from any
structures, motor vehicles, etc. Orient the airplane so that it is facing
crosswind with the muffler outlet facing downwind. Install a restraint
suitable for the airplane, with the engine running, to be held in place
without human assistance. Ensure that there are no other loud sounds
present from aircraft, motor vehicles, etc.
2. Always read the muffler side of the aircraft (ex. The right side
for upright mounted 2-stroke engines). Place the meter downwind of the
aircraft on a tripod 11 to 12 inches off the ground; perpendicular to the
fuselage at the muffler outlet; and at a distance of 3 meters (10.9
feet). Position the meter at an angle of 70 degrees from the down wind
line. Install the windscreen over the sound level meter microphone.
3: Turn the sound level meter ON by rotating the range dial to the
first position, “Batt”. Verify that the battery is good by observing that
the meter reads in the acceptable “red” range.
4. Set up the sound level meter as follows:
5. Start the engine of the airplane under test.
After the engine has been started and properly tuned, and the adequacy of
the restraint verified, ensure that there are no persons closer than 3
meters/10.9 feet to the airplane. Run the engine up to full throttle
6. Note the reading on the sound level meter.
7. Acceptable reading = 94 db (or lower).