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Re: hiss reduction and spectrograms

Subject: Re: hiss reduction and spectrograms
From: Gianni Pavan <>
Date: Thu, 11 Mar 2004 10:24:43 +0100
Great Walt!
Running a high resolution real-time spectrogram is my choice when listening 
to recordings. In this way I can see what I can't hear!  And I can check 
what I believe to hear!
It is important to look at a high resolution spectrogram (both in time and 
frequency) and to set the display dynamic range to at least 90 dB to see 
everything, from thin background noise to the loudest sounds. For this 
purpose it is also important to use a weighting  function (often known as 
"window") with no sidelobes; don't use Hamming because sidelobes spread 
over the whole spectrum; Hanning is better, but still not good enough. My 
preferred windows are Gaussian and Kaiser-Bessel. You get no sidelobes at 
all, you get the best dynamic range, though, you pay this with larger 
bandwidth (larger traces...). Of course, you can counterbalance this by 
increasing the window length and the FFT size.

Gianni


At 02.49 11/03/2004, you wrote:
>From: "Barb Beck" <>
> >
> > Another thing to remember when removing hiss from recordings you want 
> others
> > to hear is that if your high hearing is going even somewhat you can create
> > something which sounds just fine to your ears but "dead" and unnatural to
> > somebody who hears the high stuff well.  You can even find some commercial
> > stuff which has been overprocessed.
>
>Or, conversely, there are lots of folks who think their high hearing is
>perfect and adjust their recordings accordingly. Making way too much
>high frequency emphasis and poor low frequencies. There are probably far
>more folks like that than ones who, by some miracle, still have the high
>frequency hearing of their youth.
>
>Overprocessing works both ways. It's amazing how many folks will get
>into painful detail about their equipment, process the sound to their
>taste using their hearing, and don't have a clue to what their own
>hearing is like in detail. If you are haggling over the lint on the
>sound, you should haggle even more over the lint on your hearing. Get
>tested, at all frequencies, know what your ears are doing. And don't
>just test once and think it does not change. There are inexpensive kits
>available to self test that can do a fairly decent job of tracking it.
>
>I know my high frequency hearing is far worse than it was when I was
>young. It's one of the reasons why I process with a realtime sonogram
>display in the chain. Helps a lot. Also helps to deal with that
>impression there is a lot of high frequency stuff to worry about. Only
>in real close recordings, not the norm for nature recording. And even
>there it's a minor component.
>
>A sort of hiss or ringing is another thing that can happen to folks
>hearing when they age, or abuse their hearing. I expect some are trying
>to remove something that's not in the recording. Find what you want to
>remove in a sonogram first. If it's not in the sonogram, it may be you.
>
>Walt
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>

--------------------------------------------------------------
Gianni Pavan
Email 
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel        +39-0382-507874
Fax        +39-02-700-32921
Web       http://www.unipv.it/cibra




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"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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