For me not an obstacle, because I do not mind the hum, but we must not expect a zero-noise device. When installed in a wall arises in the room a faint background noise that is hardly noticeable during a conversation or at room loud music. For me is a pulse point that the device both an AC circuit between two different circuits (even dimmable, once only) as well as a normal off / can be produced on-with-dimming.