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Re: dither

Subject: Re: dither
From: Walter Knapp <>
Date: Tue, 10 Dec 2002 14:56:17 -0500
Rob Danielson wrote:
> Hi Rich--
> It's possible that the low number of bits that get used in a low 
> level field recording may be the bigger culprit.  I've gone this 
> route which, indeed, you may already be doing. I carefully equalize 
> as I normalize every field recording trying to minimize the "resonant 
> grunge" with 2-3 passes of  Waves Q10 or Waves Ren 6 (which I find 
> smoother). The noise is not in perfectly discrete bandwidths but it 
> does have some more noticeable concentrations in the low to lower-mid 
> range. Important to eq at the speaker level I intend to play it at. 
> After the amplitude is high, I do the head/tail fades when burning 
> the file to audio CD using most of the 16 bits for most of the fade. 
> I also notice that after I have a saturated, fat file, the processing 
> outcome if I must do additional equalization or file mixing comes out 
> much closer to what I heard in preview mode. I believe all waves 
> plugs dither in 32 bit.
> Rob D.

I'm not inclined to buy in so big to the low end being somehow unique in 
number of bits actually used. A high intensity sound that has little 
dynamic range will be just the same. And in most cases we are really 
talking sounds that are only about half way down in the dynamic range, 
not stuff way down at the bottom.

For instance my Portadisc has over 120 dB dynamic range. If I record 
with 10 dB headroom that quiet sound that's down at -50 dB below the 
louder stuff is half way down. Still quite a lot of bits to work with. A 
reality check is to isolate some of those quiet calls and do a gain 
adjust to bring them up and then listen to them, often they are as rich 
and complete as the stuff originally recorded up at the top.

In the dynamic filtering I've played with it's rare that cutting stuff 
below -70 dB has any effect at all. Typically when doing this my cut 
point is between -45 dB and -55 dB, though that varies.

The dynamic filter I use most of the time works on all frequencies at 
once. It would be nice to have a filter that combined a multi-band eq 
with dynamics. As it is most eq just moves the gain moving the whole 
range at once. In my case being able to remove, say, loud insects at a 
certain frequency range while preserving the lower level ambiance at 
that range is what I'm talking about. Or maybe being able to set the 
upper and lower limits of the dynamic range for that band that will be 
passed would be a good way to have it.

I would certainly agree that much of the noise we deal with is in the 
lower frequencies, but this is a different issue. Bit depth is sound 
intensity. A frequency filter will change intensity, but is not 
specifically filtering along the intensity line.

I do a similar process, though I don't use Waves software. I work along 
several parameter lines to remove unwanted sound. Cutting along 
frequency bands is one and probably the most used. But it's also 
possible to remove parts of the dynamic range selectively. And then we 
get into active noise filters which you can "train". And I also will 
"filter" along the timeline to remove some unwanted calls, sometimes 
substituting a equal slice of time from where there is no call.

I think probably a first step if moving into high end equipment is to 
look at your software and make sure its working a larger bit depth in 
it's processing. That will help a lot, and it's not a universal property 
of all software. Sometimes it's even settable.

Walt




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