ORIGINAL: pe reivers
We measure at 7 meters distance, officially the mean of four, plane and meter at 1.2m height.
Max wind speed three m/sec for valid measurements, no reflecting objects near the site, and measure over short grass.
At this distance we have 80 dB(a) max, and a few centimeters more or less than 7 meters do not affect the measurements much.
Here is a setup --per the FAI requirements - for pattern flying --
-the meter as noted -is a RS I have had for many years and is for all intents and purposes "good enough".
On this hard packed salt/mud - we performed the tests from all points and met (barely) the published requirements
to do this:-- The ZDZ40 F3A was running a 20x12 ZDZ prop -wooden - in low 6000rpm the exhaust system is a Carbon fibre full tuned type (Ed Skorepa) and the all composite fuselge was carefully taped and tightened and shimmed etc -to eliminate all buzzing and rattling --the fuselage sounds--sounded awful in the air and had to fixed to meet the sound test
the test -by the numbers -is a POS .
But -part of the rules - so we did it -by the rules.
None of the in cowl gassers have a chance of meeting this test done correctly.
Power wise- this plane is a rocket but appeals to a very limited audience - the entire setup is expensive.