BIT-RATES, FILE SIZE AND RECORDING MINUTES
The following table gives an approximate comparison of bit-rates and how they affect the length of the recording over a 100MB file.
If you're already using Audacity to edit your recordings, it makes sense to use it for encoding as well. To do so, you will need to install the LAME MP3 Encoder add-on. Encoding itself is a simple procedure. Just choose the “Export as MP3” option from under the “File” dropdown menu. The bitrate for the exported MP3 tracks can be changed from “Preferences” under the “Edit” dropdown menu.
The LAME encoder lets Audacity export tracks as MP3 and you can choose the bit-rate yourself.