Using Audacity's fade out effect, you can add professional fades to your audio files with minimal effort. The fade out effect will gradually lower the volume on the section of audio selected, reaching silence at the very end. The fade out tool is almost entirely automated, making it straightforward and intuitive enough for beginners and professionals alike. The fade out tool is found in the Effects menu, with Audacity's many other tools.
Highlight the section of audio you want to fade out to silence. The larger a section you select, the longer and slower the fade effect will be.
Click "Effect," followed by "Fade Out."
Finish your other edits, then click "File" followed by "Save Project" to save the project file, or "Export Audio" to save the file as a working audio file.
Audacity has a few other fade out options that are slightly different: Cross Fade Out, Studio Fade Out and Adjustable Fade. Studio Fade is a slightly smoother fade, while Adjustable Fade gives you fine control over the fade's duration and other features. Cross Fade Out is misleadingly named, as it is isn't a true crossfade between two clips but rather a different type of the standard fade to silence.
Exporting your files to MP3 requires that your computer has the LAME MP3 encoder installed, as Audacity doesn't natively feature MP3 encoding. A link to the LAME encoder is included in the Resources section.