Hello, and first of all thank you guys for Audacity.
I have been doing recordings using hammerhead rhythm station, and pod farm in Audacity, I have up to 20 or so layered tracks (guitar/drums/bass) on a song, and when I listen back to the mix I get like a very faint sonic or so crackle or static on some parts, I have singled each track and get no crackle, all together crackle. I have tried noise reduction/click fix, and so on, on most of the instrumentation, and still there is a crackle way on top. Does anybody know if in equalization if I can tweak a frequency to pull the crackle out.
You missed one. When Audacity plays all your tracks it just adds 'em up. It’s a simple arithmetic process. No effort is given to keep the addition from causing overload distortion.
Click just above the MUTE button on all your tracks with the Shift key pushed to select them all (there may be a faster way to do this). Then Effect > Amplify: top number -1 > OK.
All the tracks will drop 1dB (an invisible change) and I bet all or most of the distortion will vanish. If it all doesn’t go away, UNDO and choose -2dB.
Here it is. Edit > Select All.
This is going to be a problem when you export the show to “something:” Music Player, Music CD, Internet Posting, etc. etc. They are all going to overload way worse than Audacity and you are going to have to dance to keep your musical mix and still have clear sound.
Or maybe not that simple…
Example: 4 identical tracks at 0 db or amplitude 1. This gives an overall amplitude of 4. That’s equal to double twice the gain and brings all tracks to 12 dB in total.
A reduction by 1 dB won’t be enough for this case. All tracks should add upp to one, this makes 1/4 = 0.25 for each track. This means that each track should only have a gain of -12 dB and that’s therefore the number for the amplify effect.
Too true, but we’re not talking about two exactly identical test sounds. We’re talking about guitar, drums, bass, rhythm, etc. etc. etc. Chances of any of them lining up to create overload is pretty slim. Plus, a 12dB reduction in the volume of the piece is going to be noticed in the performance by anyone.
I’m going on the idea that this problem has been “sneaking in” to the show and while a 1dB or 2dB change may not be enough to solve every problem, if the damage decreases, you have identified the culprit and it’s clear what to do.
If you get to -12 and it didn’t help, then the problem exists elsewhere.
Since I haven’t spread enough cheer around, it’s also possible you have more than one problem.
If the tracks are not related, the amplitude increase for mixing two tracks is in average 3 dB (instead of 6 dB).
Exporting to 16 bit will clip of the higher peaks (above 0 dB). This distortion is much less obvious for tracks that are not correlated, the occasional peaks are simply not wide enough to be noticeable.
However, if there are some offending passages, you can use a limiter to clip the peaks and smooth the wave form a bit instead of just let the export simulate a hard limiter (or clipper).
You can always look how much you’re above 0 dB by:
- selecting all tracks (Ctrl-a)
- mixing down to a new, additional track (Ctrl-Shift-m)
- calling the amplify effect on this new track alone
You can delete the “Mixed” track, once you’ve got the value.
As I said before, sometimes you can get away with +3 dB when there are only spurious peaks, but it is better to aim for 0 dB (or less) and use a limiter to bring up the volume again.