Clean up and restoration of old or poor recordings is a large topic. Many papers have been written and patents applied for in this area.

I don't think dam will do what you want. Even though you can probably use Csound to do this, it might require a lot of coding to get useful results. If you want to pursue it, start with a simple low pass filter to remove the hiss, and see where that gets you. Two or more dynamically controlled filters are another possibilty.

You did not say what platform you are on. If Windows, try using the Noise Reduction function of Cool Edit. (http://www.syntrillium.com) It really works quite well.

If you have a lot more of this to do, you look might into some of the specialized software packages such as the ones from Cedar (don't have a URL), DC ART 32 by Tracer Technologies (http://www.enhancedaudio.com), or any of several plug-ins of various formats. They are not cheap, but worth it if you intend to do a lot of work in this area.

Hope this helps.

-David.

-----Original Message-----
From: Kurt S Nelson [mailto:kurtnelson2@juno.com]
Sent: Thursday, August 19, 1999 3:33 PM
To: csound@maths.ex.ac.uk
Subject: cleaning recordings

Dear Csounders:

I am attempting to clean some noisey soundfiles using the dam opcode.
The signal (a piano piece off a CD) is not much above the noise floor of
the original recording.  Hhaving not worked with compression or expansion
much in the past, I am having a hard time selecting values for the
threshold and compression ratios that result in a sound much better than
the original.  Can anyone suggest any other opcodes or techniques for
audio cleaning (maybe the term "de-essing" applies here)?

This is a project I am doing to practice for cleaning some old speeches
on reel-to-reel tapes, and to educate myself in general.  Any suggestions
would be greatly appreciated.

Sincerely,  Kurt Nelson

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Hi all.  I don't think I've posted here before although I've been
subscribed for quite a while.  I'm a sound designer but only the tax
department call me that.

Regards audio restoration, SoundHack gives an excellent result using
spectral dynamics gate ducking.

I've done some film restoration through various realtime Cedar units and
they work, believe me, especially the De-Hisser, and to a level that
exposes the underlayer masked by noise.  The best approach to noise
removal is to do a little at a time and keep re-evaluating at each pass.

Cheers

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