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Re: Odd acoustic effect

Subject: Re: Odd acoustic effect
From: "Avocet" madl74
Date: Thu Apr 12, 2012 3:52 am ((PDT))
Jos=E9,

Nice recording. For starters, you've got two of the World's
best mics there and they are working well together as an M-S
pair. I can't hear a wall pickup and if it was there it
would show up as an out-of-phase effect. Theoretically there
should be a peak from the wall 100cms away at around 170Hz.
(340 / 2.0m) There is a small peak at 200Hz but perhaps the
stream is not producing much at those frequencies. There is
a big dip in the spectrum at 20Hz which may be due to the
landscape and may worry a passing elephant. :-)

If you have a wall reflection at higher frequencies, it
would show up on the fig-8 S mic which has an equal back
response, but you may be losing that if the mics are low and
in grass. Next time listen as you move the mics around to
see what the wall is doing.

The first thing I did with your track was to undo the
bass cut with a 6dB/octave bass lift. The HPF was fine for
the birds but not good for the stream, making it sound too
thin. There isn't a sharp resonance like I got (and
incidentally haven't heard since after dozens of plane
passes) but there are hollow gurgling sounds from the stream
which are probably from the rocks or whatever the stream was
running over. I've got a steep stream here which plays
tunes.

My preferred mix (Using Audacity) is to copy the original
track, use the 6db/octave HPF on one copy and a softer HPF
on the other (mine was HPF800-1-2-3 which falls at 1dB for
the first octave, 2dB for the next and 3dB per octave
thereafter) I mixed in the second (low frequency) water
track at about -12 to -6 db.

David

David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce







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