When I first read this question I thought of the movie "Dogma" in which God (played by Alanis Morissette) speaks with such an awesome voice that any mortal who hears it implodes from the overwhelming magnitude of the sound. To be honest I kind of like that idea. As a Buddhist I am prone to believe that "God" is a inseparable aspect of all of our perceived aspect as well as a link to that which its beyond or perception. In that respect I suppose God might sound like everything. In my imagination, God sounds like nothing. God's a nothingness that is vast and miniscule simultaneously. The most substantial omnipotent/ubiquitous nothingness that has never existed. It's a quite that renders the listener deaf. It's a silence that knows me and knows best.
However, I still like that image put into my mind by "Dogma". There is something beautiful about a creator who's beyond the scope of his children. Who must be cautious not to destroy his mortal creations. I like the thought that maybe God doesn't speak to us directly because to do so would destroy us; that God has to let us figure it out for ourselves or else we'll never learn; that even God can't remove our frailty or govern the magnitude of his/her/its awesome power.
Of course this is all wild speculation. Your guess is a good as mind. Maybe God just sounds like the mundane. The bad stuff as well as the good. God's the sound of food sizzling on the grill and the sound of the airline clerk apologetically informing you that your luggage has been lost a second time on the same trip. Would anything meet your expectations? Or would any sound at all just be disappointing?