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<DIV><FONT face=Arial size=2>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? </FONT></DIV>
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<DIV><FONT face=Arial size=2>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.</FONT></DIV>
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<DIV><FONT face=Arial size=2>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.</FONT></DIV>
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<DIV><FONT face=Arial size=2>Earl</FONT></DIV></BODY></HTML>