Exported MP3 messed up on some platforms, perfectly fine on others

Hi all, I’m trying to put together my radio show, thus am mixing multiple tracks in Audacity 2.4.2 on macOS Mojave. The audio sounds perfect when I play it in Audacity itself. However, once I export as an MP3 (extreme quality) and try and play with quicktime audio player, the audio is jittery and cuts in and out. When I play the mp3 in iTunes on my mac, it sounds even worse, with harsh/metallic sounds. When I upload to Google Drive and play it on my mac or iphone, the mp3 sounds perfect again! And when I play it on Apple Music on my iPhone, it also sounds perfect. When I import the mp3 back into audacity, it still sounds good.

I’m worried about sending the mp3 to the station, and it sounds bad on the air, given it sounds bad on some platforms but good on others. What’s going on?? WAV files sound perfect on most platforms, but I must have it as an mp3 for the station. Converting the WAV to mp3 makes the file sound bad again.

Thanks for any help!

Is your show mono or stereo?

I’m worried about sending the mp3 to the station

No. Don’t do that until we resolve this.

Is your show mono or stereo?

What he said. One blue wave on the timeline or two?



OK. Step one. We make a protection backup. File > Export > Export as WAV, 16-bit. Move that file somewhere where you’re unlikely to step on it by accident.

Tracks > Mix > Mix and render to a new track.

This should give you your stereo show on top and under that, a single blue wave mono track. Solo that mono track (button on the left) and play it. It should be damaged in the same places that your troubles are damaged.

Let us know. Different fixes depending on how this comes out.


Hold it. I got the numbers wrong.

As we go.


After you make your protection file.

Tracks > Mix > Mix Stereo Down To Mono.

That will give you a single blue wave. Play it and see what’s there.


What we expect is that some of the files you used to mix in your show are damaged. In stereo (two waves) this can give you a slightly odd-sounding show (some sounds coming from behind you) but the instant you mix down to mono or play the show on a mono-mix sound system, the broken parts of the show may vanish or turn to trash.

The stupid joke is this only happens when the client gets the work.

If this is it, you get to decide whether you want to try and fix the Edit Master, or go back to the original sound files, fix them, and recreate the show. This isn’t fun.


Aha. When I mixed down to mono, I am now hearing the cutting in/out in audacity.

So, if I’m understanding correctly, one or some of the tracks I am using are damaged, but the problem is only noticeable when the mp3 is played mono? So, the reason the mp3 sounds bad on some platforms and good on others has to do with whether it is being played stereo or mono on the platform (google drive vs. quicktime audio vs. itunes, etc.)?

I guess I will have to get to figuring out which of the tracks are damaged. Is there a way to prevent this in the future — e.g. try importing every track as WAV or something. I also am curious as to why the problem doesn’t present when I export as WAV.

Thanks again for all your help, folks.

You may be a victim of a convenience. The latest Audacity convert to MP3 also mixes down to mono. It’s a little checkmark in the dialog and it defaults to checked.

Any conversion of your stereo show to mono will reveal this problem. File format is irrelevant.

The Left and Right channels of some of your work are put of phase.

If you magnify the damaged tracks, you may see the up and down motion of the waves are exactly out of step.

Screen Shot 2020-09-04 at 14.57.09.png
Pay attention who which parts of the show are like that. Music? Only your voice? Something else?

Open a damaged stereo track. Use the drop-down menu on the left > Split Stereo Track. Select the top track > Effect > Invert. Select the top track > Menu on the left > Make Stereo Track. Done. If you magnify the waves again, most of the waves will be going the same direction. This track is fixed.

You can do that to all the damaged tracks and then mix the show again.

Can I predict the past? Did you use a vocal microphone adapter like this one?


That one is famous for creating “magic” voice tracks like this.


It’s good to track this back to where the damage is coming from. The two inspection methods are mix to mono and watch the waves mostly vanish, or magnify the waves and see that they are out of step with each other.

If you listen on good headphones you will start to recognize the “sound” of the damage. The sound has a hole in it or sounds like it’s coming from behind you. Normal sound is slightly flat and coming mostly from straight ahead.

This is a stereo/phase sound check.


Post back if you find the problem. It’s good if we know as many trouble spots as possible.

Also remember this is a forum, users helping each other, not a help desk.


It’s not unusual to play that sound clip and discover your stereo sound system is actually mono and the fourth voice vanishes.


Hmmmm. Now that I’ve tried both methods, I’m left a little more confused.

Mixing a track down to mono produces a high-pitched version of the track — almost as if it was sped-up.

Inverting the top track produces something entirely different, almost like it is watered down (I’ve attached a photo of what it looks like uninverted).

Either way, I don’t think I’ve diagnosed my problem. I’m not sure what you mean by “coming from behind me”, but it does sound like mini holes in the audio. It sounds static-like, but it’s faint. It just becomes very noticeable when I play in something like iTunes or Quicktime.

Anyway, I’ve listened to my original files in Quicktime to confirm they didn’t start damaged, and they sound great! Something about importing these files in audacity are causing these holes.
Screen Shot 2020-09-04 at 3.59.58 PM.jpg

Time to throw a lot more information. What’s the show? What are the parts, how are they mixed, who is performing, and on what?

We can only do generic troubleshooting just so long before we’re just flapping in the breeze.

I knew the problem had to be phase and Left - Right distortions because that’s one of the few problems that can create “magic” shows. It plays here, but it won’t play there for no reason we can tell.

Did you play my test sound clip on your devices? “This is my voice on the left…” Did you get any surprises? Are you listening on headphones? The fourth voice , the one intentionally messed up, sounds really creepy on headphones and that can be one of the ways to tell if you’re going to have trouble with your own production.


Sorry for the delayed response, it has been a weekend full of troubleshooting. I have solved my issue, but I still don’t know what the exact underlying problem was.

It is simply a radio show! I was mixing mp3 files of songs with voice recordings from a zoom call. The voice recordings are imported as m4a files. There are quite a few tracks – 10ish, and the final product totals an hour.

The test clip you attached sounded fine on my devices, but sounded a little weird once I imported then exported it via my original .aup file.

I spent a lot of time isolating each audio track, trying to figure out the issue. They each sounded fine when listened to elsewhere, and even when imported into a different .aup file. However, once they were imported into the .aup that I was originally working with, things sounded weird.

So, to solve my issue, I simply copied all my tracks and pasted them into a new .aup. Everything sounds good again! I don’t know why the original .aup file was corrupted/messed up. Audacity did crash a few times while I was editing…

Do you still have that original .AUP file?
If you do, you could attach it to your reply (See: https://forum.audacityteam.org/t/how-to-attach-files-to-forum-posts/24026/1)

Audacity did crash a few times while I was editing…

Do you know what a “doorknob moment” is? A person has been to the doctor’s office for a checkup and for the most part passes very well. They’re leaving the office and with their hand on the doorknob, turn and say “I throw up blood every night before I go to bed. That’s not important, is it?”

Audacity doesn’t just crash a few times. I’ve never had Audacity crash and have only had one instance where Audacity created a damaged recording for no known reason. In years of use. So there is something profoundly wrong to cause that.

I hope Steve has some ideas. This fails one diagnostic trick. If somebody paid me a lot of money to cause this problem intentionally, I’m not sure I could do it. Why would a Project cause phase cancellation problems, only on some sound files, and then give up the good fight and crash multiple times? That’s super unusual.


I do note one thing from your illustration. You have a wild mixture of technical standards. The bottom track is Stereo, 48000 we assume from a video. 48000 is a video sampling rate. The top track is Mono 32000. I don’t know of a common sound system which uses that. Answering machine? Voice Response System? “Your call is important to us…”

If there’s enough tracks in your show, we assume at least one is going to be the common Stereo, 44100. So Audacity will be jumping through hoops to accommodate all those different technical standards in real time.

What’s the Project sampling rate, the number in the far lower left?

Screen Shot 2020-09-08 at 3.00.23 AM.png
Do you have trouble with some tracks playing at the wrong speed? Are you applying Effect > Change Speed or one of the other Change tools?