If you own the legitimate Steam version:

If you are playing on a modified client (such as Plutonium or Redacted):

Ensure the sound bank file actually exists in the correct path. It should typically be in: Call of Duty Black Ops II / zone / all / cmn_root.english

For over a decade, this error has plagued fans of Treyarch’s 2012 masterpiece. While the game remains a favorite on Steam and Game Pass, this specific audio bug can make the game unplayable. Fortunately, the PC community has cracked the code.