Audacity is easily the best free audio editor:
http://audacity.sourceforge.net
I don't know about automatic detection of breaks. I've always found those features to be too inaccurate. It takes less time for me to just look at the audio waveform visually, and cut it when there's a long flatline.
Audacity has some excellent noise reduction tools, too.
Moving this to the tech forum. Also remember to try and make thread titles as descriptive as possible, to encourage others to participate.
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Update: I found this Audacity multi-track export info elsewhere online:
Most likely, you will have multiple tracks or songs in your recording, and it makes sense to export them as multiple files. Ensure you have all the tracks recorded, using the Fit Project button on the Edit Toolbar. The number of ‘boxes’ or ‘balloons’ should correspond to the number of tracks. Using the zoom controls, click in the gap between songs, choose Tracks-Add Label at Selection. Name the labels as per your song titles.
Select File-Export Multiple, choose MP3 Files as the Export format. Click Options to use the built-in presets to select the quality of the MP3.