sound meter

[ed.schummer]

Couldn't agree more.  Most of these meters work pretty well when measuring
relative levels of pink noise, such as in calibrating control room levels to
a SMPTE standard, or such.  The problem comes up when there is a dominant
frequency that is much louder than the others, as often occurs with our
planes.  We once tested a bunch of these meters, and although on average
they were pretty good, I have seen as much as 6 dB difference from one meter
to another at single frequencies, both meters calibrated to the same level
with pink noise....

Ed


----- 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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