Running the latest Audacity and the latest Mac OS
I recorded two separate audio tracks on different devices. One on a digital recorder and one on a laptop using Audacity. I mistakenly recorded the Audacity one in 44100hz and the one on the recorder in 48000hz.
When I try to sync them, they slowly grow apart. Any tips or tricks in getting them into 48000 with out distortion?
I poked around and tried a few things last night, but figured it would be worth asking the “experts” 
Please don’t forget to give us all three Audacity version numbers (see the pink panel at the top of the page). Quite a few people who say they have the “latest version” do not. Only our site is guaranteed to have the latest version http://www.audacityteam.org/download/mac.
You can try Effect > Change Tempo… or Effect > Sliding Time Scale / Pitch Shift… on one of the tracks, assuming both tracks already sound at the correct pitch.
Sometimes it works better to adjust only the start and end to sync, rather than apply the effect to the whole track.
Gale
If, as you describe, the problem is due to the devices running at slightly different speeds, (very likely), then the effect to use is the “Change Speed” effect.
http://manual.audacityteam.org/man/change_speed.html
For precise alignment, set the “Current length” units to “hh:mm:ss + samples”, then set the effect to stretch the length of one track to match the length of the other. To find the precise length of the other track, select it, then look in the “Selection Toolbar” http://manual.audacityteam.org/man/selection_toolbar.html
Great! Thanks… This is what I was playing at, but maybe just need to fine tune it.
Appreciate the responses.
And a quick note, I don’t think 44100 and 48000 have anything to do with it. Audio editors “know” what both of those are. Chances are much more likely the two recorders weren’t expensive enough. Would you know if your 44100 recording was really running at 44101 because of manufacturing tolerances? That wouldn’t show as an error until you made a long show and then tried to compare that show length to something else—which you did.
I just compared two ten-minute, 400Hz tone clips, one made at 44100 and the other made at 48000. Both opened in Audacity 2.1.2 at the same time. Attached is the magnified end of the “show.” Exactly correct.
Koz
I’ve seen cases where the pitch on an external recorder was dead right at a slightly wrong speed, so Change Speed made it sound microtonal when perfectly aligned. That was what I thought might be happening here. Either way, we have presented all three methods.
Gale
Well, the 44100 was Audacity itself. The 48000 was a Zoom H4 digital recorder.
I’ll be recording another hour tomorrow. I will be making sure both recordings are going at the same rate, and we will see if there is any difference.
Thanks again.
44100 was Audacity itself.
Not exactly. 44100 was handled by the computer. Audacity is a slave to what the computer is doing. It’s a toss-up. Who is more likely to be accurate, the Mac internal codecs or the Zoom? That’s assuming nothing is broken. That’s hard. They both do this very well. I have no guess.
The movie people spend serious bucks to make sure the movie camera and the completely separate sound recorder are in perfect sync with each other during a shoot.
If you do find the error is still there, it’s probably the same error, so you can make one, standard correction to everything, forever. Write down that correction.
the pitch on an external recorder was dead right at a slightly wrong speed
That gives you the production island. The music is perfect as long as you never leave the island/recorder. The instant you try to “correct” it, compare it to anything else or move it, you’re hosed. And that gives you > SMPTE, EIA and other standards organizations.
Where would we be without 44100?
Koz
There is a darker, more evil possibility. One of the performances has tiny gaps in the presentation and got shorter that way. That’s not unusual, particularly with Windows laptops hanging on with just enough horsepower to do all their jobs.
But you’re on a Mac… With a dedicated Zoom…
That doesn’t work with you…unless something is broken.
Koz