http://lifehacker.com/5902802/ever-w...-youre-driving You can click on the link part way down the page to bring up a list of states/legal status.
And quite frankly, I hear people with their stereos blasting way way louder than I EVER play audio books in my headphones. I can easily hear what is going on around me with my headphones in, no way those people with the blasting music can!! If I can hear their music in my car, how much can they be hearing?? Shoot, I can hear some people's music in my HOUSE as they drive by!!
S