Q: Why is there a humming noise when using a headset on a VoIP phone?
A: That is a common problem on VoIP phones due to a missing ground connection. The noise is caused by the metal microphone tube and a metal part of the headset, respectively, which act as antennas. There are two simple solutions:
1. Connect the phone to the switch with a shielded Ethernet cable + connector (make sure your wall socket/switch/hub has the shielded socket connected to the ground; most of the switches available on the market do).
2. In case your network environment is not grounded you can use the phone as a switch and connect the second port of the phone (PC port)to the Ethernet card of the PC by means of a shielded Ethernet cable. The PC card is grounded by default.