The sound engine relies on specific DirectX 9.0c files that aren't always included in modern Windows 10 or 11 installations.
Black Ops 2 is an older title and sometimes struggles with high-definition audio formats or missing playback devices. The sound engine relies on specific DirectX 9
If the above troubleshooting steps do not resolve the issue, you may want to try the following advanced solutions: The sound engine relies on specific DirectX 9