When I import any of my stereo mixed files, they play back at a much higher volume.
And there a many ‘red’ clippings shown.
Nothing was clipping when I worked with, and saved the mix.
I used the default settings when doing the mixdown.
Anyone know why this is happening?
Alan
Sorry for not including in post: Audacity 3.1.3, Windoze 10
The individual tracks may not clip, but collectively they can.
If you “mix and render to new track” you can see if that is the case, before saving.
Mixing is done by summation. Analog mixers are built around summing amplifiers but they have level controls for each input, plus a master level control.
With two tracks you can prevent clipping by lowering both tracks so neither one exceeds -6dB (50%).
Or you can export as floating point WAV which essentially has no limits. (You shouldn’t leave it that way because you can clip your DAC when you play it.) Re-import the mix and it will show red for potential clipping. Then run the Amplify or Normalize effect to bring down the volume and export to the format of your choice.
Note that if you export to MP3 some peaks get higher and some lower and you’ll often “see red” if you open the MP3. MP3 can also go over 0dB but it does have limits. If you want to avoid that, normalizing to about -1dB before exporting will usually keep it out of the red.
Before mixing, I play all tracks to make sure there is no clipping.
After I mix and render to a new track, there is still NO sign of clipping.
After saving the mixed track (WAV), I import it.
Now the amplitude is way higher and there is clipping all over the place.
As suggested by DVDdoug, I lowered the gain on all tracks to keep the level at -6db or less.
I mixed to a new track. Again, no signs of clipping and I then saved the mix.
Now when I import the mix, there is no clipping, so I’ll keep everything at -6db or lower. Great.
However, again, the amplitude is still higher than before I saved the mix. Up to 0db.
I have to turn my speakers down every time I play a saved mixed track.
I still don’t understand why is that happening.
Alan
This would happen if you do Export > WAV at this point. Instead Mix and Render to a new track, just do Mix and Render (replacing the previous audio), OR, do Export > Selected Audio.
I tried both suggestions. Now the mixed files no longer show clipping.
Since I want to save my edited tracks, Export>Selected Audio works best for me. Then I pan the individual tracks back to center and save the edited tracks.
I still don’t understand why mix and render to a new track causes a higher gain/clipping.
Thanks for the help.
Alan
I still don’t understand why mix and render to a new track causes a higher gain/clipping.
Like I said, mixing is summing (addition). [u]Digital audio is sampled[/u] with each sample representing the amplitude at one instant in-time (i.e. 44,100 samples per second, or whatever your sample rate).
When you mix, the 1st sample from each track is added together, and the 2nd samples, and so-on… When you add you get bigger numbers (higher positive and higher negative numbers). Since the data is “random” (uncorrelated) sometimes you’re adding a positive to a negative (effectively subtracting) but there are lots of positives added to positives and negatives added to negatives that the peaks and the overall volume increase.
If you duplicate a track and mix it with the original you’ll get the same thing with twice the amplitude (+6dB). As you may know, our hearing is logarithmic (or “proportional”) so it doesn’t sound twice as loud. If you duplicate a track, invert it, and mix with the original it will “subtract” to silence. (Amplifying is done by multiplication and adding every sample to itself is the same as multiplying by two for a gain of +6dB.)
And if you just think about it… 100 people singing is louder than one person singing! 
Soundwaves also sum (or subtract) in the air but it’s continuous analog instead of discrete samples.