> there is an article somewhere called the stereophonic zoom. the mathematics
> of microphone patterns, angles between them and distance is very nicely
> detailed there.
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Umashankar,
The problem with a "stereophonic zoom" is that is not like a camera zoom.
You do get a relationship between a front object angle and the resulting
image angle, and this is important for good stereo. The big difference is
that with a camera zoom, unwanted objects are cut off, but with a sound
"zoom", unwanted sounds get overlaid over the final image, often out of
phase.
M-S mics are often called "zoom mics" because altering the S signal adjusts
the apparent width of the stereo image. You often find these on video
cameras consisting of a forward facing gunmic and a sideways fig-8. The
gunmic gives a good noise elimination for sounds to the sides, above, below,
and rear, but as soon as you fade in the S signal, you get a lot of stuff
which is not in the video picture, almost all of it out of phase.
The link I gave before:
http://www.degruyter.com/dg/viewarticle.fullcontentlink:pdfeventlink/$002fj$
Message: 002faoa.
Subject: 2011.36.issue-2$002fv10168-011-0026-8$002fv10168-011-0026-8.pdf?t:ac
=j$002faoa.2011.36.issue-2$002fv10168-011-0026-8$002fv10168-011-0026-8.xml
on page 9 gives graphs of object/image relationships for various mic
combinations under ideal conditions. However, they didn't show what happens
past the "sweet area" of the stereo mics. That's fine for controlled studio
recording but not for field recording where sounds come from everywhere.
David Brinicombe
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