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Gear / Technical Help => Post-Processing, Computer / Streaming / Internet Devices & Related Activity => Topic started by: page on May 25, 2009, 07:10:03 PM

Title: Feedback reduction help needed (sample inc)
Post by: page on May 25, 2009, 07:10:03 PM
I try not to dicker around with what I tape, but the feedback at the beginning of one song is enough to make me recoil and wince. What all do people do to try and remove such foul effects?

I am not necessarily trying to get it perfectly removed (bonus points if you come close), but at least to the point where my eyes don't roll back in my head.  :P

(sample named .txt cause TS allows SHNs, but not FLACs....)
Title: Re: Feedback reduction help needed (sample inc)
Post by: Brian Skalinder on May 26, 2009, 12:29:15 PM
FWIW, I'm unable to play or decode the FLAC after removing the .TXT extension.

Foobar says "unsupported format or corrupt file", and FLAC says "ERROR while decoding metadata, status = FLAC__STREAM_DECODER_END_OF_STREAM".  My other FLACs play / decode just fine, so I don't think it's something on my end.
Title: Re: Feedback reduction help needed (sample inc)
Post by: page on May 26, 2009, 12:52:31 PM
Ok, lets try that again. 16bit sample this time and less of the music surrounding it, but still has the problem.
Title: Re: Feedback reduction help needed (sample inc)
Post by: Brian Skalinder on May 26, 2009, 04:32:53 PM
I usually just compress the section of feedback so it isn't ear-splitting on playback.  We've all heard feedback at performances before, and I find I prefer the familiar feedback itself - albeit compressed so it's not earsplitting - to the unexpected and more unnatural artifacts resulting from attempted removal (see / listen below for the latter).

Alternatively, you might try using a spectral view editor and/or notch filters to manually remove the feedback's fundamental frequency (in this case, ~1500 Hz) and harmonic frequencies (integer multiples of the fundamental...e.g. approximately 3000, 4500, 6000, etc.).  You could even go crazy and tediously attempt (and probably fail) to manually remove the inharmonic frequencies (non-integer multiples of the fundamental), as well.  (Personally, I don't think it's worth the effort.)  In either of the above cases, IME you'll still have plenty of artifact leftover.  But you may find it less offensive to your ears.  For a quick and dirty example, in the attachment I've very swiftly and not very carefully removed the fundamental frequency and harmonic frequencies using Adobe Audition's spectral view.  As you'll hear, plenty of artifact remains, but to some it may prove less offensive to the ears.

I suspect in short order someone else will chime in about the wonders of iZotope RX, with which I have no direct experience.
Title: Re: Feedback reduction help needed (sample inc)
Post by: ghellquist on May 26, 2009, 05:01:37 PM
What about this?
http://trombonisten.se/new/NEW.wav

Several passes with spectral cleaning in Samplitude pro.

// Gunnar
Title: Re: Feedback reduction help needed (sample inc)
Post by: Brian Skalinder on May 26, 2009, 05:07:33 PM
What about this?

Ah, much better!  Didn't even know SAM offered a spectral cleaning tool.  Still not going to upgrade from SE, but good to know it's there if I ever want to upgrade.
Title: Re: Feedback reduction help needed (sample inc)
Post by: page on May 26, 2009, 05:13:50 PM
I tried to general compression and the notch effect last night.  :(

I'll check out both samples when I get home. Thanks  ;D
Title: Re: Feedback reduction help needed (sample inc)
Post by: page on May 26, 2009, 11:13:42 PM
I opted for the ParametricEQ with a tight band and did notch filters (-15db or so) on each band up to around 12khz. You can still hear it, and there is some fuzz from the artifacts, but its a happy medium that makes it listenable without induced pain on a track I rather enjoy.

Thanks folks. I appreciate the help.