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When The Impulse Filter Doesn't Work

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  • When The Impulse Filter Doesn't Work


    Sometimes the impulse filter (EZ Impulse Filter) can not fix a real nasty record scratch. When this happens to me, I sometimes have trouble finding the noise and fixing it with the I key. I have found a method that helps me and I'll pass it along for others.

    Background : For 78 records, I have a multifilter that is my "standard" for clean up. This multifilter has an Impulse filter first, then L+R, then some continuousnoise filters. I have been just taking the raw recordings and running the multifilter FIRST and then manually fixing the song AFTER the filter has been run.

    Problem : For really long impulses, the EZ Impulse filter doesn't always fix the "pop". The result is that the "pop" turns into a more longer impulse because of the filtering action of the CNF filters and others in my multifilter chain. The original short impulse causes the filters to "ring" and the result is a sound that is hard at times to find and fix, since it's now longer in time duration.

    Note : This is just the "impulse response" of an electrical network.

    Fix : What I now do, is using classic edit mode, run the multifilter on the original recording. I listen to the result in the destination window. When I hear a "pop", I switch to the source window and use the "I" key to fix the impulse. Note : You have to be in Sync mode to have the noise line up from Destination to Source. I find that the original impulse in the source window is much easier to find and fix since it doesn't have any ringing in the original. Also, the sound can be usually fixed so nice that you can't hear the impulse afterward.

    Last edited by Marc Hildebrant; 06-01-2012, 04:46 PM.

  • #2
    Cool solution. I usually do this kind of thing in fast edit and keep going back and forth between the edits using the history viewer. I think your method is less prone to making mistakes and undoing one too many edits.


    • #3

      Indeed, it would be hard to find the correct place to "fix" if I was using the fast edit mode. With the classic edit, I just look above the noise to see what my multifilter missed.

      Some of the times, the EZ Impulse will fix up a really big impulse and manual work isn't needed, but, there have been times when I have looked for a long time to see what gave me a "thump" in my cleaned up recording. By having the source right above the "thump", I can zoom in and easily fix the cause. I'm still amazed at what the "I" key can do, even with quite long passages.