fade in phrasal verb ( see also ↑ fade )
to appear slowly or become louder, or to make a picture or sound do this
fade something ↔ in
Additional background sound is faded in at the beginning of the shot.
—ˈfade-in noun [countable]
FADE IN
Meaning of FADE IN in English
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012