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Sent: Thu, January 20, 2011 6:41:35 PM
Subject: Re: [Nature Recordists] Introduction of a new member - Expanding t=
he
dimension of recording natures sounds to surround sound
Joel,
Welcome. I'm a retired BBC Mobile Sound Recordist and I've just taken
up serious nature recording and it's a whole new ball game. I'm
finding this list very useful.
> I live by a lake not far from Austin TX. The nature
> sounds where I live at are heavenly particularly in the morning and
> evening.
> I have always wanted to mount microphones outside the house and feed
> the
> sounds into the house.
It sounds idyllic. What's the background level like? I've got woodland
with a small stream which is a problem with distant birds and
reverberation. I roll off the bass background according to the species
I've recorded, but the real killer is wind in trees. You will need a
good overall windshield for your array as well. I use separate blimps
with "yeti" covers but this separates the mics more than I would wish,
defocussing the centre image because of relative phase shifts.
Profesionally, I used the ground effect when I could. Over a
reflective surface
getting the mics as low as possible catches the boundary effect which
enhances the directivity. Water does this well but you need an
intermediate surface or board to conduct the surface effect to keep
the mics safe. If you've got good water birds this may pull them in
well. The surface effect also helps with wind and aircraft noise.
> Currently I am working on a custom 360
> degree microphone array in which the sound will be converted at the
> source
> to digital signals.
The BBC use an array like this for the surround sound version of the
music Proms, mixed with the usual array of close mics with adjustable
delays. The mixing desks are digital so mics provide a digital feed to
them but the bit rate is high, depending on sample rates. I think 24
bps is standard to give a wide dynamic range. This array is four
bidirectional mics in the middle of the auditoriu, and they can be
processsed digitally to give four discreet pickup areas, but I've been
retired some years and haven't got indide information.
I'm recording analogue and at 16 bits which is a different ball game
but it sounds OK, but I'm making inroads into my hard drives. I set
the recording level to 10dB over noise giving a large headroom. The
usual digital recording lineup is -14 dB peak below 100%, but I'm more
like -24 dB but can pull this up without loss of quality. At what
stage are you setting levels?
I'm running a pair of MKH406's on 100 metre cables and I can't hear
any degradation even on cheap cable. The mics survive rain in the
blimps but this may be a problem with a digital array unless you have
more predictable weather than in SW England. :-(
Best Wishes, David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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