There are these times in life when you know you are up a creek.
Well, I found some interest in my post as now I have two of the best
current people in the world on parabolics commenting here and I don't
completely agree with either. What to say?
As you scan across a target with a parabolic such as the sun, you see
the focal point scan side to side as well. It may not be a perfect
focus at 2" off center but in that sound is physically longer than
light I suspect it is a bit more forgiving. That said I know I
should not go to far into the deep end with either Randy or Klas as
they both can tear me apart with what they know.
I will show two stereo examples of separated mics in a parabola
without a barrier in the center.
First is ~300kb:
http://home.comcast.net/~richpeet/1827.mp3
Thrasher on one channel and Grasshopper Sparrow on the second. Not
for the ones who can not hear high pitches.
The second example is more of just a description.
A recording I made straight up in the air of a Horned Lark. I only
needed the one strong channel. So I inverted the channel that was
weak on the bird and summed to mono with the channel that was strong
on the bird. The result are these stats.=20
Single main strength channel not summed.
Peak -.36
Min RMS -33.52
Max RMS -7.75
Avg RMS -21.29
Weak channel inverted then summed to mono
Peak -7.10
Min RMS -48.53
Max RMS -13.05
Avg RMS -30.18
What this comes down to is that this stereo technique does have some
applications for noise reduction as well.
Rich
--- In "Randolph S. Little"
<> wrote:
> NatureRecordists,
>
> This "Coloration" thread regarding parabolic microphone systems
caught my attention to the point of bringing me out of long silence
on this group.
>
> Perhaps I missed it, but nowhere did I see mentioned explicitly
what is actually quite obvious from the facts as stated -- that is,
that the "coloration" is primarily in the off-axis sounds which are
basically the background noise of the environment. Add to this the
low frequency cutoff of the reflector system, and you have the
classic "parabola sound."
>
> The subjective effect of faithfully capturing all the high
frequencies of the on-axis signal while stripping away the highs from
off-axis directions is to make the signal seem crisp yet mellow. The
crispness owes to the fact that the highs of the (on-axis) signal are
no longer so masked by highs from the (off-axis) background. The
mellowness owes to the fact that we have stripped the harsh highs out
of the background.
>
> BTW, with Rich's stereo parabolic microphone system, given that the
mikes are 4" apart, I conclude that neither mike is at the
reflector's focal point, so that the system's gain vs. frequency and
direction is probably not properly described by the formulae cited
earlier in this thread.
>
> Good recording,
> Randy
> -----
> Randolph S. Little <>
> 111 Berkeley Circle, Basking Ridge, NJ 07920-2009
> Phone: (908)221-9173 Fax: (908)630-0871
> URL: http://rsl.home.att.net
>
> [Non-text portions of this message have been removed]
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