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Re: noise reduction techniques

Subject: Re: noise reduction techniques
From: Dan Dugan <>
Date: Sun, 4 Jan 2004 00:41:16 -0800
Rich Peet wrote,

>  > 1. When there is no audio that is important above 15,000 cycles I
>>  drop the gain in this region by 50% to 75% (6db to 10db) on a slope. 
>>  It does not effect the overall recording and hides the ragged
>>  compression of this area that can be seen on a spectral display which
>>  is the signature to many that the recording was a MD.  It really does
>>  not change the heard audio any, but for those that pay attention it
>>  fools a few of them into thinking they may be looking at a 24 bit
>>  recording with >100db s/n.  I use it with restraint but hey if it
>>  makes someone think that I am better and have higher tech equipment
>>  then I do then it was worth the effort.  This part of the edit is
>>  vanity.

And Walt commented:

>Unless they use sonograms, few would find the MD effect you speak of.
>Nor is it consistently there. If it is in your equipment, then there may
>be some other fault with the equipment. It is certainly not consistently
>there in all the sonograms I've done on MD recordings.

I monitor my work with Spectrafoo instruments, and the effect that 
Rich mentions is quite apparent in spectrum analyzer displays of 
perceptual coded stuff. It doesn't show on sonagrams. It's a 
sure-fire indicator that you're listening to a perceptually-coded 
recording, even though you usually can't hear anything strange. I'm 
going to play with the rolloffs as Rich suggests, but there isn't any 
audible need for it--as he says, he does it just to clean up the 
appearance on an analyzer.

Because I work in theater, I often have to do noise removal 
processing, and I keep buying expensive software that does that. Even 
the best is problematic, and I rarely do more than plain vanilla 
equalization/filtering to my nature recordings. I would only use 
dynamic noise filters on nature sounds if I was composing, mixing 
cleaned-up specific sounds over a natural bed.

-Dan Dugan


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