When I connect my headphones there is no sound
When I connect my headphones there is no sound but they do work in the rest of the computer
Check the audio output device in the game's options and set it to your headphone/speakers.
I had this issue. Once you've made sure your ear/head phones are working in other games go back into Blops 2 and go to options, settings, sound, sound device and make sure it's the same as your head phones.