I want my exported MP3 file to sound IDENTICAL to my project track. The quality changes every single time! It has more feedback, more noise in the background - everything that makes it worse! I’ve tried improving the quality, switch to a WAV file, reducing the quality. I’m out of options here. 
What is the NORMAL STANDARD EXPORT to have your music file IDENTICAL to the project track??? No changes in quality at all!
Please help Thank you so much!
Beaker
MP3 is a “lossy compressed format”, which means that it discards some information when it is encoded in order to reduce the file size.
For “perfect” quality you can export as 32-bit float WAV, but there are two problems:
For “almost perfect” quality, export as 16-bit WAV. This is generally the recommended format, and is the default for Audacity.
The files are still big, but only half the size of a 32-bit WAV.
16-bit WAV is supported by almost all other audio programs.
16-bit AIFF and FLAC files will give the same quality as 16-bit WAV, but WAV is more widely supported by other programs.
MP3 is a “lossy compressed format”
My Spidey Sense is telling me there’s something else going on. MP3 compression doesn’t make a song get noisier. If anything it has the opposite effect. Noise tends to vanish as irrelevant to the enjoyment of the performance.
How are you listening to the exported file? What happens if you export a WAV (Microsoft) 16-bit and then play that in Audacity?
I went round and round with a new computer that just would not pass simple sound quality tests. Turns out the System People left a Windows Special Effect running in the soundcard by accident.
What’s the show? Exports tend to follow the Time Line selections and steering selections. If you don’t want a particular track to appear in the show, MUTE it with the buttons on the left.
Does your show have a lot of corrections, filters and effects? Is it mono (look to the left of the timeline)?
Describe the performance.
Koz
Did the exported WAV and the exported MP3 sound the same? I mean as each other, not compared to the Project.
Koz
It has more feedback, more noise in the background
Go-ahead and try those suggestions and answer Koz’s questions, but I’m not sure what you’re describing…
Feedback is that squeal you get from a PA system when the sound from the speakers feeds-back into the microphone. You can get something similar when recording on a computer, but it’s usually an echo and it can get louder-and-louder until it’s an out-of-control mess.
Noise is unwanted sound, such as hum, buzz, hiss, or a dog barking when you’re trying to record. Noise tends to be most-noticeable when the signal is quiet or when there is silence. If you’re recording a loud guitar, the noise usually gets drowned-out as long as the guitar stays loud.
Distortion is damage to the signal. It’s usually worse when the signal is too loud. Clipping is the most common kind of distortion. You can clip your digital signal if you go over 0dB.* Your digital-to-analog converter (playback), your analog-to-digital converter (recording) and “regular” WAV files are all limited to 0dB. Or if you try to get 110 Watts out of a 100W amplifier, that distortion is also clipping.
Since Audacity itself uses floating-point it won’t clip. You can have a file that goes over 0dB and as long as you’re not playing at full volume you might not clip your DAC and it might sound fine. But, if you export as a regular WAV file or if you make a CD, you’ll get clipping.
MP3 and other lossy compression give you different kinds of distortion that are not easy to describe/define and that are not related to loudness.
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Thank you Steve. I’ll give that a try soon.
You’re right, Doug! Feedback was the wrong word to use. Noise like humming, buzzing, static - whatever you want to call it is what I’m mostly hearing when I turn it into any file on my PC. Same speakers/volume by the way. It went from something you would hear on the radio today to something you would hear FDR talking about in a Fireside chat in 1934. It’s like . . . where did all this extra noise come from?? It’s not in the track at all.
My performance was this . . . I’m performing on a keyboard with multiple orchestra instruments (I did the Beetlejuice Main Theme). It’s not distorted thankfully, it just sounds like the MP3 and WAV files were saved on a 1980 long distance phone call or something. Meanwhile I play the track on Audacity and it sounds like a cassette player quality - not so bad.
No Koz, the WAV file sounded better than the MP3, but it’s still not perfect. I went with a high bit file. I’ll try the 16bit as Steve recommended as soon as get back to my PC.
What I tried to do should have been a very simple task where I performed on a cassette tape and want to convert those songs to digital. The recording to Audacity sounded just like the cassette, so I didn’t need any fancy stuff done to it. I was satisfied with my very first recording. With no changes whatsoever to the track, I went to export it cause it’s perfect. Then I get the sound of Woody when you pull his string in Toy Story in the MP3 file. wth??? Where did the record player sound come from?
Again, I’ll give the 16bit WAV file a try soon. Thank you all so much for the advice! 
Beaker
It’s like you’re describing a system from Mars. None of those things is supposed to be happening.
Given a fresh recording and reasonable MP3 setting, you should not be able to tell the difference between WAV and MP3.
There’s supposed to be no difference between the Project and the exported file.
None of these processes increases noise.
etc, etc, etc.
That’s why the blank looks across multiple time zones.
Koz
Something similar happened to me and I searched everywhere for a solution and couldn’t find one on here - but finally figured it out on my own! I got so frustrated on these boards because I found people with similar issues to mine but everyone commenting was like “that shouldn’t be happening, what you’re describing makes no sense.” No kidding! That’s what I was thinking, that’s why I couldn’t figure out how to fix it!!
ANYWAY - here is what worked for me:
I had an audio file that played fine in the Audacity program, and fine when I exported to WAV, but when I exported to mp3 it sounded so weird and distorted you could barely hear the speaker in the audio. I realized that when I was exporting to mp3, in the export settings I had selected “force export to mono.” When I changed this to export mp3 to joint stereo, it worked fine. However I needed a mono file. So in Audacity I clicked on the name of the audio file to open up more options, selected “split stereo to mono,” which split it into to waveforms. I deleted one of them, then exported again as an mp3 forced to mono. It worked fine! So I would suggest checking if you are exporting to mono or stereo and seeing if changing it makes a difference.
The same thing was happening to me, and I didn’t know any other way to describe it either. Obviously none of those things is supposed to be happening, that’s why we’re struggling. My issue ended up being that I didn’t realize I was exporting to mono instead of stereo. I’m not an expert on this stuff, and don’t always know the right words to explain everything. But I needed a mono file and had to split audio to mono, then delete one of the two waveforms before exporting to mono. Something similar could be happening to the original poster here.