I am trying to create sounds for a railway museum and I have several Mp3 files of trains arriving and crowd noise. Is there a way to record say two tracks in mono so that I would have the crowd sounds over the train sounds [laying via an MP3 player…like a busy station.
If you have multiple (stereo or mono) tracks open in Audacity they will be mixed when you export.
If have two mono tracks and you want to mix them to a stereo track, there is a little drop-down arrow to the left of the waveform and you can select Make Stereo Track.
Note that mixing is done by summation so you can get clipping (distortion). That doesn’t apply if you’re making a stereo track from two mono tracks because you are not mixing the left & right channels together.
If you are mixing two tracks you can use the Amplify effect at -6dB to bring down the levels before mixing. Or, you can export as floating-point WAV (which can go safely over 0dB), then re-import the mix and use the Amplify or Normalize effect to bring-down the mix. Then export again to your final format.
I have several Mp3 files
Just FYI - As you may know, MP3 is lossy compression. When you open an MP3 (or other compressed file) in Audacity (or any normal audio editor) it gets decompressed. If you re-export as MP3 you are going through another generation of lossy compression. You may not hear any quality loss, (especially with “crowd noise”) but the damage does accumulate so it’s something you should be aware of. If you are stuck with MP3 originals, try to minimize the number of times it’s re-compressed.