At this point, we might do well to re-read some early posts in this thread,
such as David and Dan, below.
Dan, I'm still working on my response to your plea to avoid noise reduction
-haven't forgotten you at all.
I'm presently accumulating some data using David's 'under the bed clothes'
test with the PMD 661 and various transducers at gain settings from 0 to
Message: 10.
Subject: So far I have an NTG1 and a peizo crystal(with Jensen DI) on a tin can
top. Both yield -80 to -81 dBFS at a gain setting of 0. I thought the Peizo
would do much better. Am I hitting the published 65dB S/N wall? I'll
carry on with some quieter mics I have this week (with a spreadsheet to
follow), but I'm thinking that actually using more than 16 bits is a
challenge solved only by superior technique and money.
Keith
On Tue, Dec 4, 2012 at 12:26 AM, Dan Dugan <> wrote:
> **
>
>
> > With very quiet backgrounds and low noise pro mics and inputs or
> > mixers, 24 bit recording theoretically gives you another 8 bits, which
> > is nice but probably difficult to justify. I say "theoretically" as
> > the dynamic range at 24 bits is 23 times 6dB, or 138dB which is much
> > greater than any mic input stage could ever come near. With studio
> > mixers, you don't want to worry about noise, so 24 bit is used, but
> > with wildlife recordings, this increases file sizes.
> >
> > Thermal noise of the air is around 0phons (it's frequency dependant)
> > and the best pro mic systems will have an "excess noise over thermal"
> > of around 12 dB. Ear damage starts around 90 phons, so if you need to
> > record this level without adding noise, use 24 bits, but you won't
> > find a listening setup which can reproduce this range. :-)
>
> 24-bit codes are written, but the actual signal-to-noise in the real worl=
d
> is 21 bits maximum due to the analog parts of the signal chain. Fade-outs
> in a DAW will use all the bits, which is why you must add dither noise at
> the very last stage when reducing to 16 bits for CD distribution.
>
> I use 24-bit recording because it gives you extra headroom to work with.
> You can record low for safety in the field and boost it in post without a=
ny
> loss of quality. Now that storage is larger and cheaper, the larger file
> size doesn't matter much.
>
> -Dan
>
>
>
--
Keith Smith
Keith Smith Trio, Northern Lights =96 Altai Khangai - www.keithsmith.ca
Photography - www.mymountains.ca
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