If you are within the warranty period you can get a replacement. Same problem here - had it for about 5 months. Worked fine, then today noticed humming noise. On phone with D-Link now (going on 25 mins) -- and 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
They need supervisor approval before they can send the RMA email - that takes time too.
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.