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Audio problem, need audio expert help!

Discussion in 'Fan Films, Fan Audio & SciFi 3D' started by keithabbott, Aug 29, 2002.

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  1. keithabbott

    keithabbott Jedi Grand Master star 4

    Registered:
    Aug 7, 1998
    Hey guys. For those of you who work with audio a lot, I'm hoping someone can tell me what's wrong.

    I have a particular person who has sent me several varying wav and mp3 files. Using two different mics, the same problem keeps developing.

    I've attached an image of the problem from Sound Forge here:

    http://www.riseofnobility.com/problem.jpg

    For some reason the resting recording rate is well above the Inf. level, which is causeing some noise and pops when you start or stop playing the file. I need to know the likely cause.

    Is it the recording level? Is it the sound card? Or perhaps a software/settings issue?

    Any help would be greatly appreciated. ANd if there is a way to correct this in sound forge (by centering the sample), please let me know.

    Thanks
    Keith
     
  2. JEDIBYKNIGHT

    JEDIBYKNIGHT Jedi Padawan star 4

    Registered:
    Jan 17, 2001
    I don't work with audio a lot...

    But I've had this problem before (pops, noise...) and I solved it by changing the frequency (I was using files and exporting the final results at a different frequency).
    So when I changed the final output frequency to 44.1 Hz, everything sounded good.

    Hope it can help :)
     
  3. brokenglassltd

    brokenglassltd Jedi Youngling star 1

    Registered:
    Jul 6, 2002
    Knight is probably right. Usually when sound pops it's because of the sampling rate. Digital sound is 44.1 Hz, while radio is 32 Hz. This means the sound is sampled 44,100 times per second. Pretty fast, huh?
    The levels would not cause the entire clip to pop. When a sound clips in Sound Forge, the program translates that into a click or pop. Yet your levels are fine. Unless the levels were set so high during recording, there is no way this could happen.
    My guess is that the recording was set at a lower sampling rate. Go up one setting, but it may speed up the recording though.
     
  4. keithabbott

    keithabbott Jedi Grand Master star 4

    Registered:
    Aug 7, 1998
    I think you're right. I've been able to duplicate the problem. I set my recording profile to 24,000 khz and my recording level a bit high and was able to get the same results.

    When I lowered the mic level and uped the khz to 44.1 I was able to even out. Of course, that's also relative to being closer to the mic with the lower recording level. I think she was much further away that I would have thought, plus speaking softly.

    I think that might be the problem. But any other helpful advice would be great. If anyone has any.

    Thanks for the help guys.
    Keith
     
  5. brokenglassltd

    brokenglassltd Jedi Youngling star 1

    Registered:
    Jul 6, 2002
    No problem.
     
  6. MasterZap

    MasterZap Jedi Padawan star 4

    Registered:
    Aug 11, 2002
    Uh *the pain*

    You are OBVIOUSLY not audio people. Bwahaha. Giggle. Sorry.

    You have what is known as a "DC offset", a name whish is a holdover from analog audio, meaning that "no audio" is not "0 volts of electricity" as it should be, but there is some voltage there already.

    In digital, it means your zero level aint on your zero line.

    There are several ways to fix this:

    1. Find the "DC Offset" fix function in your audio app, if it has one.

    2. Hi-pass filter the audio (i.e. put on an EQ plugin and kill all super-low
    frequencies, say, below 5 hz or whatever...
    sinze a DC offset is technically a 0hz sound)

    3. The third method is: Dont "do" anything, just make sure to FADE IN and FADE OUT the clips every time, to avoid the pops.

    /Z
     
  7. keithabbott

    keithabbott Jedi Grand Master star 4

    Registered:
    Aug 7, 1998
    Thank you very very much Master Zap. Yes, I'm an audio person....I just don't know that much about audio software ;) hehe. Go figure. The thing is, I'm a producer...not an engineer. hehe. Is that an excuse? :p

    Again, thanks for the help. I appreciate it.
    I ended up doing the DC Offset which worked, but I still had to fade in to get the initial pop out. Very quick fix.
    Keith
     
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