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<DIV><FONT face=Arial size=2>John:<BR><BR>Yes, it is very tricky. The
problem is finding the known reference. That's why we have to re-calibrate
so often even with a "quality" meter. AMA told me at the time that the
calibrator device itself was about $500.00... Of course, it was designed
specifically to fit over the mic of that particular brand of meter, and may not
be very accurate with another meter unless a custom head was built to hold the
calibrator exactly the same distance from the mic while blocking all outside
noise sources...</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV> </DIV>
<DIV>Tony Stillman<BR>Radio South<BR>3702 N. Pace Blvd.<BR>Pensacola, FL
32505<BR>1-800-962-7802<BR><A
href="http://www.radiosouthrc.com">www.radiosouthrc.com</A></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=jpavlick@idseng.com href="mailto:jpavlick@idseng.com">John
Pavlick</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">NSRCA Discussion</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, February 16, 2005 7:31
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: Sound Level meter
requirements</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=210220201-17022005>Tony,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=210220201-17022005> This is all very interesting. Even in the short
time I've spent looking at these meters I noticed some questionable areas.
That's why I asked if there was a more specific set of test criteria /
procedures. It seems to me, that even under controlled conditions, a GOOD
meter might not produce repeatable results. It is of course very important to
calibrate to a reference (i.e. 94dB / 1KHz), then measure. Without doing that
you can't take accurate absolute measurements. Also, Unless the spec. is
written to allow for tolerance of the meter (most of the ones I've seen are
+/- 1.5dB), sometimes you'll read (too) high and sometimes you'll read low,
even with the same source and a calibrated meter. It's probably more important
to have an accurate means of re-calibrating the meter rather than having a
meter that has a tighter tolerance. Taking reasonably accurate measurements
relative to a known reference should be acceptable, I would think. That's
why a band tunes to the keyboard if they don't have an electronic tuner handy.
A modern electronic keyboard can be considered an accurate reference for
pitch. </SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=210220201-17022005>
<P><FONT size=2>John Pavlick<BR><A href="http://www.idseng.com/"
target=_blank>http://www.idseng.com</A><BR> </FONT>
</P></SPAN></FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN
class=210220201-17022005> </SPAN>-----Original
Message-----<BR><B>From:</B> discussion-request@nsrca.org
[mailto:discussion-request@nsrca.org]<B>On Behalf Of
</B>tony@radiosouthrc.com<BR><B>Sent:</B> Wednesday, February 16, 2005 7:25
PM<BR><B>To:</B> discussion@nsrca.org<BR><B>Subject:</B> Re: Sound Level meter
requirements<BR><BR></DIV></FONT>
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<DIV><FONT face=Arial size=2>Del:<BR>The problem with all meters I know of
is that they all change! I was the first one in the USA to work with
the FAI in establishing how a db check would actually be done in the
field. I did the first ones at the 1983 US Team Selections in Rough
River, KY right before the 1983 World Champs. As I was the assistant
CD for the WC, AMA wanted me to gather the data and learn how the system the
FAI had designed would really work in the field. We found that even
expensive db meters developed drift.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The expensive versions used by AMA have to be
adjusted about every 4 hours, as they can drift 1/2 to 1 1/2 db in that
period of time due to temperature changes. That is the problem with
any meter. Unless you have a calibrator to adjust the meter, it is
really pretty worthless in getting an accurate measurement. As long as
+ or - 5 db is OK, you don't need to worry. However, if you are trying
to meet any model noise requirement out there, your really spinning your
wheels. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>Tony Stillman<BR>Radio South<BR>3702 N. Pace Blvd.<BR>Pensacola, FL
32505<BR>1-800-962-7802<BR><A
href="http://www.radiosouthrc.com">www.radiosouthrc.com</A></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>