You aren't alone except when you are alone. And when I ride alone I bring my Shuffle. I can still hear the traffic. In fact I prefer the slightly muffled traffic noise. Full on traffic noise is a little too loud and nerve racking. If I'm riding with others, I leave the shuffle at home.
I'm not the greatest singer, but also sing aloud as I ride. Maybe that is why I have to ride alone as often as I do.
skm