I was riding my minecart system on Creative around on one of my first worlds generated in 1.1), but when I got to the high speed bit using powered rails, the sound started trying to restart every tick, creating a rather painful jarring sound. Even when the Minecart slowed, the sound persisted until I got out.
How to reproduce
1.Make a rail
2.Make powered rail section to speed up (I think mine was six powered rails long)
3.Ride Minecart along the track while riding
4.Cover ears (Or you could just turn the sound down, I guess.)