The easiest way of choosing a level of compression for your MP3 files is to use the Preset Quality slider.
The Preset Quality slider allows you to choose from several levels of quality and resultant file sizes. As you choose higher quality, the file size goes up as well. On the other hand, lower quality presets will be smaller and easier to send over the Internet.
Preset Bit rate Channels
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Phone 16 kbps Mono
Shortwave 24 kbps Mono
AM Radio 32 kbps Mono
FM Radio* 96 kbps Stereo
Voice 64 kbps Mono
Radio 112 kbps Stereo
Tape 128 kbps Stereo
Hi-Fi 160 kbps Stereo
CD 192 kbps Stereo
Studio 256 kbps Stereo
The default is CD quality (192 kbps, Stereo).
* Note that the FM Radio bit rate is higher than the next preset quality, which is Voice. Voice is @ 64 kbps and FM Radio is @ 96 kbps. The reason that there is a discrepancy is because Voice is mono and FM Radio is stereo. If you were to divide the FM Radio bit rate in half, you would have 48 kbps per channel, which is lower than the Voice preset.