sound meter

[Ed White]

We had a noise sensitive field.  We used the Radio
Shack sound meters (98 dB at 3 feet, this is about 10
years ago).  We ignored calibration.  It worked
reasonably well because nobody got hung up on 97.5 vs
98.5 dB.  Basically the approach was to make a
"reasonable" attempt to get close to 98 dB and then go
with it.  We also had a mechanism for relief in that a
club noise committee could be petitioned for relief on
the rule for a individual airplane basis if the person
had made an honest and reasonable attempt to meet the
98 dB.  (meaning willing to buy or make a new muffler
at reasonable cost, ie, $25 was not too much to spend,
$100 was too much to spend).  

It all worked well and our noise complaints stopped. 
Note that we didn't have any pylon racers or other
loud airplanes in the club, mostly 40-60 size sport
flyers and a few pattern flyers.

Mufflers are better today but may be more expensive,
especially for larger IMAC class airplanes.  The level
you choose depends on what you are trying to acheive
and what kind of airplanes your club flys.  Most
members came to like the lower noise levels that came
with the 98 dB rule, but I'm not sure there would have
been great value in going lower.

Today we have a non-noise sensitive field but we kept
the 98 dB rule anyway.  It hasn't been enforced at our
new field and I'll bet many members aren't even aware
of it.  

I can't imagine a non-quantitive way of doing it.  How
people perceive loudness is a science in itself
because there is such broad variation in what sounds
people find disturbing.

Hope this helps,

Ed


--- Xavier Mouraux <xavier.mouraux at sympatico.ca>
wrote:
> Hello guys,
> 
> I am trying to have my club using some sort of noise
> rules. I would like to
> know what level and what procedure are used in your
> clubs. Is there a
> non-quantitative way of doing this in a club without
> creating troubles ?
> Also, how do we calibrate the tester ?
> 
> Thanks
> 
> Xavier
> 
> 
> 
> ----- Original Message ----- 
> From: "David Lockhart" <DaveL322 at comcast.net>
> To: <discussion at nsrca.org>
> Sent: Monday, April 26, 2004 9:54 PM
> Subject: Re: sound meter
> 
> 
> > To me, the bottom line on the current noise rule
> (largely unchanged since
> > introduced) is that we no longer have 105 db
> planes that offend the
> > neighbors.  And from my experience over the past
> 15 years working with
> > "quiet" setups - an honest 94 db on pavement is
> not that difficult to
> > achieve.
> >
> > In practice, application of the noise rule is not
> without problems - but
> it
> > is not that difficult to copy setups that are
> known to be quiet, and
> > following some basic rules of thumb will keep the
> noise under the limit -
> > and avoid noise test failures at major contests.
> >
> > The last thing I would want to see is a shift from
> a quantitative noise
> > measurement to a qualitative noise measurement -
> I'd hate to see placement
> > in a contest determined by a bonus or penalty
> assigned by a judge to a
> plane
> > that sounded "nice" or "loud" - especially
> considering the relatively
> > uncontrolled background noise present at most
> contests (other planes in
> air,
> > engines running in the pits, etc).
> >
> > Regards,
> >
> > Dave Lockhart
> > DaveL322 at comcast.net
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Adam Glatt" <adam.g at sasktel.net>
> > To: <discussion at nsrca.org>
> > Sent: Monday, April 26, 2004 3:44 PM
> > Subject: Re: sound meter
> >
> >
> > > Earl Haury wrote:
> > >
> > > > 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
> > >
> > > Good idea, but terrible rule.  They should give
> a 5% score penalty to
> > > the noisiest 10% of planes in a class (either by
> ear or by sound meter),
> > > imo.  Measuring a plane on the ground, with
> someone holding it, people
> > > standing around, wind blowing, and the prop a
> few inches from the
> > > ground, and from a distance that doesn't
> represent the problem of noise
> > > (i.e. Shulman's electric being one of the
> loudest planes on the meter
> > > due to low clearance and gear box noise, but one
> of the quietest in the
> > > air) is a dumb way to do it.  The only noise
> that matters is what we
> > > hear while the plane is in the air.
> > >
> > > It was obvious in Poland the FAI officials knew
> the sound rule was
> > > implemented wrong, as well.
> > > =====================================
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> http://www.nsrca.org/discussionA.htm
> > > and follow the instructions.
> > >
> >
> > =====================================
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> >
> 
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