Dan Dugan wrote:
> I see your point, I was only thinking of the acoustics. How about a
> stiff wire cage?
A branch grabber.
>>The mic will see the entire parabolic on a sonic level.
>
>
> Won't there be shadowing at high frequencies? If the sound is out of
> focus, it might have a point source image in the reflector, and I
> would expect the high frequencies to fall off when that point is
> behind a post.
>
> When the sound is in focus, won't there be a high-frequency
> attenuation effect, (above some crossover point depending on the
> dimensions of the slots) as half the high-frequency signal
> approaching the microphone is reflected away?
>
> I'm also imagining resonances across the small dimension of the
> remaining tube roughening high frequency responce. Maybe an
> over-fertile imagination.
See Klas' description of what the sound focus of a parabolic is really like.
>> I've tried both
>>styles over the years and both work the same. This is just a lampshade
>>harp that's closer to the mic and 4 legged. This is a less expensive
>>method while still providing necessary mic protection and the theme is
>>inexpensive homemade parabolics that are relatively easy to construct.
>
>
> Understood. Bigger holes?
Ah a challenge. Well, I don't recommend trying this without considerable
control of the material, but I set out this morning to build the
lightest possible support from the same PVC pipe. The cross sections on
the new one are down to about 1/8" for the remaining material. I can
twist this a fair amount, though it still maintains alignment. It's
probably too light to be practical.
>>I've got the mic that it's designed to fit, and a working MZ-R30. So
>>I'll see what I can pick up in the next few days. Then we will know for
>>sure. My worry is more I might have cut it a slight bit too short for
>>accurate focus, I estimated off the Telinga setup, and the mic there is
>>in a large chunk of foam so I'm not positive of it's exact location.
>
>
> Looking forward to your reports.
It's all been gathered onto a webpage in my main site:
http://wwknapp.home.mindspring.com/docs/quickparabolic.html
Note that the sound samples are 700k + each, so you will want to save
them to disk if you plan on listening more than once. I would have liked
to use higher quality mp3, but size grows.
Most of the sound was recorded last night from 2-3AM. Two Southern
Leopard frogs quietly discussing what to do to that guy that messed up
Dry Pond Swamp for them, assorted insects, the fans of a large
chickenhouse about 800' away, and the gas turbine power plant about 2
miles away are the main players.
Those were recorded with the original nosepiece. After finishing the new
nosepiece (which is 1/2" longer to be better focus) I tried to find
something today. The mic sounds the same in the headphones. Still have
the chickenhouse and power plant, added a airplane. Jay at 400-600',
Crows 800-1000'. Insects from 50' out.
Last night I carefully aimed all around various insects and could find
no shadow of the support.
Walt
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