"Fade In" means that the audio starts in silence and gets stronger, "Fade Out" is at the end of the sound to make it lower until there is silence.

The example below shows the source audio and the audio with applied "Fade In" and "Fade Out" effects.

 

Source Audio
 
Same Audio with Fade In and Fade Out<br>Time=0.5s
 

Source Audio

 

Same Audio with Fade In and Fade Out
Time=0.5s

Both "Fade In" and "Fade Out" are useful because they allow ensuring that the beginning and the end of any audio is smooth and do not have any prominent glitches. Both might be helpful in case of custom voice records or interviews.

Use of both effects provides a better quality of output audios after splitting albums having no silence gaps. "Fade In" and "Fade Out" also helpful when Trim Silence and  Limit Duration effects are in use.

Both effects are simple to operate and applied by converters automatically without intervention. Just enable "Fade In" and "Fade Out" in Preferences / Effects window and drop your music to the main window of the converter. 

Read More: How to setup "Fade In" and "Fade Out" effects >>

A Linear Fade, the most simple type of fade, is used in converters, where the level or amplitude of the signal rises or falls at the constant rate.

An important parameter is the "Fade In" and "Fade Out" time. Most appropriate "Fade In" or "Fade Out" time can be around 0.5s. This value is selected in "Preferences / Effects" by default, and can always be adjusted.

The example below shows output audios with "Fade In" and "Fade Out" time 1s and 2s.

 

Audio with Fade In and Fade Out<br>Time=1s
 
Audio with Fade In and Fade Out<br>Time=2s
 

Audio with Fade In and Fade Out
Time=1s

 

Audio with Fade In and Fade Out
Time=2s