Propstoppers RC Club - sound level measurements

Procedure for Making Sound Level Measurements
Revision 0, December 02, 2003

Procedure 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)

Procedure:
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:
            Weighting:         A
            Response:         Slow
            Range:              90

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).