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Thread: Eliminating Noise caused by Automatic Gain Control

  1. #1

    Unhappy Eliminating Noise caused by Automatic Gain Control

    Hello,

    I am restoring/cleaning some very old lectures. The person recording used the automatic gain control which means that every time the professor stops speaking for apx. 5 seconds, an intolerable noise/hiss comes in. I have both Pro Tools LE 8 and Sound track pro (both have the waves bundle).

    The noise reduction in STP does nothing to help. We've tried messing with a few compressors but can't seem to find the right fix.

    Any suggestions greatly appreciated.
    Many thanks!
    LilC

  2. #2
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    Get the CEDAR plugin- costs a fortune but otherwise you live with it. There's no filter for bad original recording.

    Noah
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  3. #3
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    You could try the old-fashioned way - duck the volume. Not perfect, but better than nothing.
    Peace,

    Uncle Bob

    A craftsman knows how to avoid mistakes,
    An artist knows how to use them.

  4. #4
    Moderator Zwick's Avatar
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    No ducking in STP by the way but yes in GarageBand.

    Eric Peterson (AKA, "Zwick")
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  5. #5
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    You can do it manually with volume automation...
    Peace,

    Uncle Bob

    A craftsman knows how to avoid mistakes,
    An artist knows how to use them.

  6. #6
    Moderator Zwick's Avatar
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    By the way, CEDAR DNS One only runs on an Intel Mac under Pro Tools and is in the $3,500 price range. There are studios out there which provide these services.

    Eric Peterson (AKA, "Zwick")
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    It's a very old thread I know, but just thought I would add a couple of things.
    a) avoid using AGC if you are ever the one doing the recording
    b) if you have a good audio editing software then using volume automation by manually setting of levels as needed is still a great way to do this sort of stuff...even if time consuming
    c) Mentioned originally was the Waves bundle. Not sure which bundle that was as there are many Waves packages, but the Restoration bundle is excellent, and I use it all the time for removing unwanted noise from audio. It includes X-Crackle, X-Hiss, X-Hum which are all very good tools.

  8. #8
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    How about this trick? Lay the track down twice. Flip the second one 180 degrees out of phase. Compress the heck out of it until the signal (voice) is completely buried in the noise (BG). Gently mix the effected track into the uneffected track. At some point the out of phase 'noise' will cancel the in-phase 'noise' but since the out of phase 'signal' has been lost it shouldn't affect the in-phase 'signal'. It's never a perfect solution, some out-of-phase signal always seems to seep through but the results can generally be easily handled with EQ.

    We used to do this LIVE! We had a talent who did an opening standup in a hallway in front of a trophy case which was right under an AC duct. We just sent the mic signal through two rails, effected one of the rails as noted above and poof, no AC
    Remember: Nobody thinks about audio... until it's not there.

  9. #9
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    Cedar is king but iZotope RX is probably the best value http://www.izotope.com/products/audio/rx/

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