Both are less than 6 months old. One is an adapter that I got for my Raspberry Pi, the other is an iPad charger. Both do the same thing, even if I plug the USB from the charger to the USB port on the Arduino. Does it on both Arduinos (UNO and Nano).
Now that I think about it though, since my project is going in my car, it will probably receive noise in there as well, moreso than from AC I would think.
I guess I will start by trying a different wall outlet, maybe I have bad wiring in my house (wouldn't surprise me).
If I use a voltage regulator (which I will be) that should take all of the noise out if there is any, correct?