The characters speak gibberish. Ranging from randomly ordered "alien" or "foreign" words that repeat over and over again or utter gibberish that has no clear traits of any language besides sounding vaguely speech-like.
Alternate names: Gibberish voice-overs
Name variations: Nonsense
The first video game about Speech: Gibberish was released in 1988.
The general background noise that's supposed to be the hundreds if not thousands of people speaking should be ignored. Effectively, only cases where actual dialogs the player partakes in or supposedly listens in on should be counted.
This is NOT for properly used constructed languages, such as Klingon or Esperanto.
Normally these come with subtitles in proper language.