Dan Dugan wrote:
>>I would not think that would fly very far. There is a established
>>procedure for certifying noise meters that are being used where legal
>>wrangling will be involved. About doubles the price of a meter to get
>>one of these, and all it really amounts to is legal documentation all
>>the way from some primary standard to the particular meter. But, without
>>it anything that gets into court will die. And I'm sure the park service
>>stuff will generate court cases.
>
>
> I'm sure you're right about that. Do you think an amateur calibration
> system might be acceptable for scientific work? I've spent my 35-year
> audio engineering career getting professional results with consumer
> and semi-pro equipment, and I know it can be done!
If you read Bioacoustics L for a while as I did til I could stand it no
more you would know. They are almost worse than the lawyers.
However, if you are talking to more practical scientists, myself
included, I see no problem technically. Just as I said, make sure it
never has to go to court, or be looked at by the bioacoustics crowd, or
try to publish it in one of the bioacoustics journals. From my many
years doing environmental impact studies, everything connected with that
has a huge amount of legal entanglements. I've been there, don't envy
anybody wandering into that buzz saw.
I probably did as many studies for lawyers working to shoot down a study
as primary studies. It was amazing what some people would try to get
away with. I had one shopping center, on the boundary between two towns,
that I worked over the course of many years on 7 different EIS studies.
All depended on which town currently was ahead in the boundary dispute
as to which one was for it or against it. I took apart study after
study. Though the last time a bunch of us did a study no one could
attack. Or at least we were more expert than those that tried. No on
that hired us ever was really interested in the environment. A EIS stops
nothing unless it was done wrong. Man was I ever happy to leave that
business.
>>...Your 2nd line would be for the recordists to have calibrators, but tho=
se
>>cost a lot too. I'm not sure I'd trust consumer gear not to drift too
>>much. Using a calibrator at the beginning and end of the recording would
>>at least check that.
>
>
> Here's another calibration idea: A portable CD player with a speaker
> and a 20-foot string attached is sent around to recordists. The
> player produces a broad-band noise signal that the recordist records
> outdoors in a quiet location, creating a reference that includes both
> level and frequency response (of course it isn't flat, but it's all
> relative).
I'm not sure it's necessary to have calibration if you are not going to
expose it to legal wrangling. I'd not trust many of the nature
recordists to do a good job with such a task, so would want it very
foolproof.
You would probably be better to pass around a actual sound meter
calibrator. Usually they put out a 94 dB level (sometimes its other
levels) and are designed to slip over the end of the mic for
calibration. That avoids any environmental effects. Of course one
complication is that it's only 94dB if the calibrator can seal to the
mic. But that can be worked around too.
Failing that, a tuning fork at a fixed short distance might be good
enough. I'd have to try it.
You probably should grab up a sample of mics and try whatever you are
thinking of. Do it several times in different environmental conditions.
See if the mics can hold calibration at all. Won't be any use if they
can't. That's part of what you pay for with the good measurement mics,
stability. Why they tend to have metal diaphragms.
With the old meter I used we had a temperature calibration we had to
apply. The newer meter I have now has that built in. A general recorder
won't. Then there's humidity...
At least you will get to play with something new.
Walt
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