Where does Arma 2 Keep the sound files for weapons and Vehicles?

[KirovRU 10]

I'd like to mod the sounds in Arma 2 but I don't have a clue where they are kept. I have the Steam Version and there are no folders indicating their location :confused:

Kirov

[Chiv 10]

"C:\Program Files (x86)\Steam\steamapps\common\Arma 2 Operation Arrowhead\Common\sounds.pbo"

I believe that's the right file