I've heard a few posters mention the active noise cancellation above. Has anyone ever been recharging and heard what sounds like a bass competition in the trunk? I used to think I was riding next to someone with a sound system until I heard it on a single lane road by myself. And I was listening to music with moderate volume. I also noticed that the noise cancellation doesn't work as well if no music being played. Anybody else run into these problems or is this just the norm?