The “silent filibuster” is not an official part of Senate rules.
The silent filibuster results from a change to Senate rule #12, aka “Rule XXII of the Standing Rules of The Senate” that was made in 1970. It allowed the Senate, for the first time, to move on to the next bill in the event of a filibuster. So in effect there’s no longer a “talk it to death” requirement to prevent a bill from reaching a vote.
The silent filibuster results from a change to Senate rule #12, aka “Rule XXII of the Standing Rules of The Senate” that was made in 1970. It allowed the Senate, for the first time, to move on to the next bill in the event of a filibuster. So in effect there’s no longer a “talk it to death” requirement to prevent a bill from reaching a vote.