i realize this topic has been beaten to death, but the notion of riding with my ears plugged makes me break out in a cold sweat. You only have two senses that keep you safe on the bike. Riding with headphones isn't as dangerous as riding with a blindfold, but it's second-worst. I can't even estimate how many times in 40 years of cycling that I've been alerted by the sound of cars coming up behind me.
Years ago, when MP3 players were new, i remember reading a post about whether they were safe to use on bikes. Somebody answered, "I see dead people..."
Up to you, of course. But you're not immortal.