Rage did an OK job with Expendable's sound. The soundtrack is varied but unremarkable. It's repetitive and uninteresting, but it does match and help the blisteringly fast pace of the game. Fortunately, there are hundreds of
explosions, growls, yelps, and shots over the music. That's the one thing Rage did right, they filled the game with sound. When you're firing a thousand rounds a minute, you make some noise and they let you know that.
Unfortunately, they forgot the bass. Explosions don't sound weak, but they don't sound strong either. Machine guns go "chugga chugga" instead of "CHUGGA CHUGGA!" Rage should have put more oomph in the audio.
Expendable does make good use of 3D audio and it supports a wide variety of formats. If you forgot to cap a baddy from the last area you were in, you'll be able to hear him coming after you, firing an occasional burst. And as a ship flies by in the introduction cut scene, you can hear it go from one side to the other. But overall, the sound is nothing special.