Just an FYI -had this humming noise just start after about 6 months of ownership.
If you are within the warranty period you can get a replacement.
The camera worked fine, then today 5/21/14 I noticed the humming noise.
I was on phone with D-Link over 30 mins -- they walk you through everything - in order to justify that it is a hardware problem, even though you know it is a problem with the hardware.
Call 1 (877) 453-5465 push phone # buttons - 2 2 5 1 to get to the appropriate support person.
Be prepared to go through everything before you get an RMA for your replacement.
1 - volume setting
2 - reboot
3 - move to another outlet
4- Send video of the problem
They need proof and supervisor approval before they can send the RMA replacement.
I have many D-Link cameras (DCS-932l) and DCS-5010L) - I noticed that most of them don't seem to last more than a year.
Their replacement process is very rigid and not consumer friendly.
Hope this helps