Enable Silence Removal
Removes silence at the start and end of tracks without gapless metadata. This only applies to fixed frame size formats like mp3 and m4a. It's also worth noting that most mp3/m4a nowadays does contain gapless metadata as long as they were properly encoded. GMMP will work the best with music ended with LAME.
Silence Threshold
Anything lower than the threshold is considered silence and will get removed.