I have the same issue with the EVO 3d, I have to constantly go to the alarm, choose the alarm sound and adjust volume. I have to continually check it, because about once a week it goes back to silent again.
I've had more issues since the ICS update then before, and I'm ready to drop kick this POS phone for a non-android. It continuely "
Unexpectedly Resets" itself at least once a week, and my home screen icons disappear for no reason.