You know the situation: there's a lone con circling your field... you're in the tower, you've upped a GV, or you're rolling an interceptor. Yet the field is silent, even though there are 10 37mm ack guns pounding away at the circling enemy. I think it'd would add a lot to the atmosphere of the game if those guns were going "bang bang bang."
When my base is under attack, I want it to sound like an air raid... sirens blaring, guns banging away, etc. On a CV, you've got way more guns in close proximity too... that should be even more noise.
