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?
My understanding was that the on-board chargers on the early 2011's didn't have a enough noise filtering, which caused some LEAF owners to experience the line noise, but this was corrected in the later 2011's (added more noise filtering to the charger). I just had my 2011 charger replaced to fix this problem. It was a slow process to get Nissan to fix the problem but they eventually did. If your 2013 is having a problem, it could be that you have a defective charger, but I don't think it's because of a lack on noise filtering in the design of that charger unless they reintroduced the problem in the newer chargers. Let's hope they didn't.
From what I understand, the EVSEs are unlikely to be the problem. Your approach of getting a different car to plug into your Juicebox is probably going to be your best bet at initially troubleshooting the problem. It doesn't necessarily have to be a LEAF. In fact, it might not be a bad idea to try out a non-LEAF EV or PZEV. I used my neighbor's Volt to troubleshoot my problem. My LEAF would cause my solar (string) inverters to buzz loudly. When I plugged his Volt into my EVSE, my solar inverters did not buzz. I then took my LEAF and plugged it into the EVSE at his house, which also had a solar string inverter, and my LEAF caused his inverter to buzz! You would think that would have been an open-and-shut case when getting Nissan to fix the problem, but I still had to go through a fair amount of stonewalling before Nissan agreed to fix it.
Unfortunately I don't live close enough to help you troubleshoot the problem, but hopefully someone in the area can help out.
Hope this helps. Good luck!