Thanks for this thread. I think I have this same issue. The buzzing is bothering me, but my wife can't hear it and sleeps just fine. I can track the whole path of the wire from the circuit box to the vehicle along my walls and ceiling listening to the buzzing. And devices like electric clock radios are buzzing too. And if you listen right at the breaker box it kind of chirps gently while the charging is happening.
I've got a 2013, and have only had it for about a month now, so I wasn't sure if I had a problem with my house wiring or the vehicle. I've tried swapping out the breaker as well as plugging other devices in, but those make no noise. I'm charging through a Juicebox, but I doubt that's inserting any sort of noise. Has anybody heard of a 2013 with this issue? I would have expected nissan to have fixed this for 2013 model.
I guess what I need is a second car to plug in and see if it charges just fine. Anybody care to come to south San Jose near Almaden and 85 for a free charge and a sixpack of beer?