The only time I consider it rude to play music out loud is on a mountain bike trail. It seems terrible to drown out the sounds of nature in the woods. On the road, pssh. It doesn't matter. My best friend has a radio mounted to his handlebars. I use headphones. Listening for traffic isn't all that important if you just assume there is a car behind you at all times. I might use a speaker if I had one, but I don't. If someone doesn't like what I'm doing, AYHSMB