sound meter

[Troy Newman]

Calibration of the sound meters is also a very dynamic thing. It will drift
in 20-30mins sometimes. Very dependant on Temp.....We found last year that
in using some of the high end meters they would drift a couple db in what
seemed to be identical conditions.


Soooo the warning is the same as others have said its a bench mark similar
to your Tach. Because your meter was calibrated this morning, yesterday or
last year doesn't mean its still correct now. Also FAI and AMA have
different rules in how the sound is to be measured. Not only the values, but
the setup is different from the FAI and AMA classes. Read your rules to find
out how to do it.


TN

----- Original Message ----- 
From: "Ed White" <edvwhite at yahoo.com>
To: <discussion at nsrca.org>
Sent: Sunday, April 25, 2004 5:22 AM
Subject: Re: sound meter


> At work I have access to a large acoustics test lab
> and borrowed a portable calibrator.  My RS sound meter
> was off up to + AND - 3 dB.  It varied considerably
> with frequency.  At lower frequencies (<1 KHz) it read
> low by 2-3 dB, at higher frequencies (>1 KHz) it read
> high by 2-3 dB.  Pretty much varied all over the
> place.
>
> The message is don't get hung up on 95 dB vs. 96 dB.
> The RS meter will give you a ballpark absolute value,
> and as Earl said will give you decent relative
> measurements.
>
> Ed
>
> --- "Del K. Rykert" <drykert at localnet.com> wrote:
> > My radio shack soundmeter was off by almost 3 dB
> > when it was calibrated.
> >
> >         Del
> >   ----- Original Message ----- 
> >   From: Earl Haury
> >   To: discussion at nsrca.org
> >   Sent: Saturday, April 24, 2004 9:05 AM
> >   Subject: Re: sound meter
> >
> >
> >   Steve
> >
> >   It matters a lot. The rules specify dB-A, so use
> > the A scale. Without a calibrator most sound meters,
> > even the expensive variety, are really only good for
> > comparative measurements. So - use it to find what
> > makes the airplane quieter but don't get fixated on
> > the absolute number without a calibrated reference.
> >
> >   Earl
>
>
>
>
>
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