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removing background humm need help asap!!

Discussion in 'Digital Audio' started by zipper1022, Nov 26, 2006.

  1. macrumors regular

    i filmed a documentary for school and neglected to use external mics so now i have the dialogue with an annoying background hum.. is there any way to remove it in soundtrack pro or any other programs? i tried doing powerline hum analysis in sound track pro but it didnt seem to detect anything...

    i need to have this movie finished as quick as i can so any help would be useful, im posting a clip up in a few minutes so u can hear what i mean.
    thanks in advance
  2. macrumors G5


    Fast and cheaply? I think you're hoovered, unfortunately. It's way easier to eliminate noises before recording, than it is after.

    There are three basic ways:
    EQ, which will cut out frequencies of the hum, but also remove those frequencies from the desired sounds. Rolling off the bass is a good start.
    Dynamics processing such as gating an expansion - turns "down" the volume between the words of the sound track. Carefully done, it can leave the words untouched, however wherever there are words, the hum will come back in. The hum (and the 'real' background audio) pumping in and out can be distracting.
    Noise analysis and removal; this requires very clever software to "listen" to the hum, recognize its pattern and selectively remove that patttern from the audio track. This is most useful on steady-state num, can be next to useless on noise or hum that is intermittant or changes in frequency and level a lot.

    Expensive software from Bias, Waves, Cedar and Digidesign can do some stuff, but were talking hundreds or thousands of dollars per package.

    Bias SoundSoap is probably your cheapest commercial solution

    This will involve exporting the soundtrack and reimporting it -- I'm not a video guy so you'll have to negotiate that manoever with your software.
  3. macrumors regular

  4. macrumors 6502


    It can be fixed in Garageband with a the Audio Unit 31 Band Eq.
    Lower gain on some of the high frequencies to loose hiss.
    Lower gain on frequencies between 60 hertz and 300 hertz to loose the boomy background.
    His voice will have a degraded sound(more treble sounding) but it will be easier to understand if done correctly.

    I took your sample and I had no problem tweaking it in GB.
  5. macrumors 6502a



    since you mentioned Soundtrack Pro, have you tried that application's noise reduction feature yet? I am talking about the one where you first set a noise print (after selecting a portion of your sound that has just the noise), and then reduce for the entire clip? It's no silver bullet, but I use it routinely on clips with a lot of success (even though I must admit I have never had anything with that much of a hum to work with).

    You'll have to experiment with the parameters a little bit, but listening to your clip it sounds like the hum is pretty constant, and there are lots of "noise samples" that you can use to register the noise print.

    One thing I have found to be very important when using this feature is to do it as the first step to the raw captured file, before any other changes are made to the recorded audio. So if you plan to equalize, compress, or do anything else at all to the audio, do it only after you use Soundtrack Pro's noise reduction. This is also why I can't try it out for you with the sample you posted online - the audio is compressed, and that's not going to be as good as it could.

    Hope this helps - let me know if you need more detailed instructions. Curious how it turns out. Or, if you can share the original, uncompressed audio clip, I'd be happy to give it a try for you.

    Good luck!

    - Martin
  6. macrumors 601


    well, at least you know now why you should use them. for an interview like that, especially if there's no audio guy, a wired lavalier mic can work great. and we're so used to seeing it on interview subjects, it's okay for the mic to be seen (though, unlike some, i like to hide the wire behind clothing).

    a boom mic can also work well in such circumstances.
  7. macrumors 6502


    How is this... I did a really quick job in Soundtrack with a noise reduction filter and a linear phase eq. If you want detail let me know.

    Attached Files:

  8. macrumors regular

    that is soo much better
    can u please let me know what you did
    all the clips were filmed in that docotrs office so i could use very simlar attributes on all of them

    wow u really cant hear the hum at all in that one and the voice isnt too distorted.

    I am pretty new with soundtrack pro, i got it a while ago and never had any use for it until now.
  9. macrumors 6502


    here you go, these are close to the settings i used. I must have erased the original, sorry.

    Attached Files:

  10. macrumors 601


    that is an improvement, but do we all agree it still sounds like a camera mic? zipper, i bring this up only to re-emphasize the point that you should make sure the audio is correct upon capture, and not try to use heroics to save it later.

    in school, good audio *will* set your project apart from the rest.
  11. macrumors 6502


    I aggree 100%. That is why I try to make mistakes only once. But it is still important to learn little tricks like this, because no matter how hard you try to control your capture there will be lots of times when something unexpected turns up.
  12. macrumors 601


  13. macrumors regular

    yea this was a super out of the blue thing. Im still in highschool andeveryyear we have a presentation about aids and stuff so this year they asked me to change it up and film a documentary, the same day, i had to go and shoot the whole thing in the docotrs office. I dont have my own mics and stuff i usually borrow a friends, but on that short notice i coudlnt get in touch with him. The project isnt being graded or anything, and its going to be played over a very bad PA system so the sound will stink anyway. I just want it to be a bit better for personal reasons. Now im excited though because my C@D mbp shipped today and hopefully i can do some work on that before the deadline

    thanks again for everyones help
  14. macrumors 68030



    Best Mac Rumors help reply of the month.

    well done

  15. macrumors 6502


    Wow, thanks! I'm blushing :eek: .

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