sound meter

[Earl Haury]

Generally even the sound meter calibrators are +- 0.5 dB. Makes the flight zero for >94 (F3A) really a tough rule (even flying behind the flight line only zero's the maneuver)! Albeit, a fail isn't official until verified by a second meter - but generally both are calibrated with the same device, so the calibrator offset will be present at both meters. Calibrator equipment itself should be re-certified pretty often (yearly), want to bet when the Nats equipment was last certified? 

The only way to be sure is to use known accuracy equipment and target a number that allows for equipment variance. The air density at the time you make measurements will vary the results also, both from an engine output (more/less rpm) and a sound transmission standpoint. This can amount to a couple of dB, and the Muncie site is usually better air density than soggy Houston - so the noise measured is higher in Muncie. Again, allow for this in your noise plan.

The good news is that the Nats meters seem to be on the liberal side and the display is analog - making it difficult to discern the difference between 94 and 94.xx. Also the 96 dB AMA limit is much easier to attain and the penalty for missing a little not too bad.

Earl
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