Deafening Silence

• WWizards of the Coast2019-10-04
  Official Ruling
  Deafening Silence will look at the entire turn to see if a player has cast a noncreature spell yet that turn, even if Deafening Silence wasn't on the battlefield when that spell was cast. Notably, you can't cast Deafening Silence and then cast another noncreature spell that turn.
• WWizards of the Coast2019-10-04
  Official Ruling
  Players may cast any number of creature spells plus one noncreature spell each turn.
• WWizards of the Coast2019-10-04
  Official Ruling
  If you cast a noncreature spell that was countered, you can't cast another noncreature spell that turn.

Rulings via Scryfall