Now that I have my mic & preamp noise issues sorted out, thanks in large
measure to the help of Mike Rooke, I still find nature recording with
mics anywhere near home (Calgary, Alberta) to be a major source of
frustration. A small city (1M) with a very busy airport and sprawling
highways is no place for quiet ambience, especially as the prairies tend
to be quite quiet, anyway.
This has lead me toward finding opportunities to use peizo crystals
whenever possible. The first experiment was on an ant hill in a local
'wildlife refuge' (2 minutes from a busy highway and with a major high
tension power corridor through the middle of it - go figure). You can
see/hear it here
<https://www.dropbox.com/s/zi0b3w6ecorbn2p/Ants_in_Griffith_Woods_append\
ed_%28formica_aserva%291280-720.mp4> .
The stereo coherence (2 peizo crystals) is very poor and the 12.5 min
video is longer than you might like as it was made for some friends who
were wondering what I was up to, but it does provide a point of
comparison for what I did next:
This 1:16 short clip
<https://www.dropbox.com/s/d7e8cchtdujfruf/PeizoStereoBar.mp4> shows
the use of the same transducers blu-tacked to a stick of wood as a peizo
'stereo bar', if you will. The stereo coherence is much improved and the
increase in contact area with the ant hill provides a considerably
larger audio target area. I must apologize for the poor focus here. I
fumbled the camera when I was mounting it and must have inadvertently
turned off the autofocus (critical with aging eyes and a digital screen
in direct sunlight). Still, it's the audio that's of interest to me
here.
About 3 seconds in, you'll hear a 'galloping' sound. Keep an eye on the
ant about 30-40mm in from the left transducer and this will give you an
idea of the improvement in pickup area.
My first thought was to use some aluminium round bar, but the speed of
sound in aluminium is about 20x that of air. Ergo, goodbye Haas effect!
Wood is somewhat better at 10x and hopefully this tired old stick is a
little slower than that, but perhaps I should forget about Haas?
One can also make adjustments with a mid-side plugin in post -I left
this one 'as is' in that respect. Bigger peizo crystals would help,
perhaps similar to what I show near the end of the first link. For this
one, I had my HDP2 at about 9.5 and added another 30dB in post!
If anyone has ideas about a better material for the bar, I'm all ears.
Maybe a bit of rubber tubing full of water? (I like the water part, but
the rubber probably won't help.) Maybe vinyl?
This encourages me to think there is some efficacy in using peizo's or
contact mics for the purpose with a bit of extra fiddling.
Keith
Hmm. Was just about to hit send... a thumbtack soldered to a 'tin can
top peizo' a la link one, could be stuck into the end of any handy stick
of wood.
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