Static, humming, or other similar noises on VoIP calls are introduced by the analog segments of the call between two parties. This would mean something on the other end of the call is producing it (easily determined if the issue persists with certain called parties) or something on your end. It could be a headset, handset, handset cord, or any other device attached to your telephone. Static can also be introduced via the phone's power supply and can be affected by the power line it's connected to. Interference can also be introduced by wires that are improperly terminated (frayed) or that may have come into contact with metal or have wires touching. Network cables that are taped across the floor can get heavy foot traffic and fray inside the cable.

Troubleshooting Steps:

1. Rule out your handset or headset by switching to the speakerphone while the issue is occurring.
2. Eliminate any potential sources of interference that may be affecting the power supply of the phone. Light dimmers, motors, microwave ovens, and fluorescent lights could affect the power supply of the phone. Connect the phone's power source to a different wall outlet if available and test.
3. Temporarily relocate the phone to another location and see if the issue follows to rule out any local power or network cabling issues.
4. If there is another phone on-site that is the exact same make and model, try swapping power supplies to see if the issue follows the power supply.
5. If the phone is power via POE (No power supply connected to the phone), change the network port on the switch that it's connected to.
6. Utilize a power conditioning device at your workstation.