I've actually been experiencing this problem for years. No updates or fixes have been made and it turns out I'm not the only one having this issue. Before you reply, I would just like to say that the following are NOT an issue: It's not because of mods, or console commands, or a corrupted BSA, and I've reinstalled New Vegas, verified integrity, etc, and the problem remains. The most I've figured out is that at some point during my playthrough, something gets corrupted and the player voice will no longer function during power attacks. If I save when this happens, and I'm not aware, that savegame is permanently corrupted. There seems to be no way to fix this, and the only solution I've found is to load a previous save where I could recall it working. This seems to be an issue within the engine. Is it possible that a mod could be created to mute/unmute the player voice on command?