Have you checked the Options / Sound from the main menu?
I usually turn the Music down so I can hear the crew, and I'll notch the Radio volume down a pinch else that has a tendency to blast you out of the conn also. I do not alter the 3D Sound Channels, because that causes issues on every one of my computers, so I don't know if that is old sound tech that is no longer valid in the 'modern' Windows, or what. It does take some fiddling though to get a balance with the rest of your system. If that's not it, and you're not on Silent Running as pabbi suggested, then look to see if you have something with your sound system customized for the game.