Headphones get quiet when opening game

Hey, I have recently recieved new Razer Blackshark V2 Headphone (the ones with the USB). But since then, whenever I open a game, for example Modern Warfare, everything gets quieter then before. With this I do not mean my audio which I can control myself, but just my headphones. This is really annoying, even if I put my volume on max it is still pretty quiet, but as soon as I close the game it is all back to normal. I have looked through all the settings but I cant find a setting which will let me disable something like this. Is this on purpose, and if so how can I make it stop? Thanks for helping