said by SLC 96:Sounds like an issue with the inside wiring. The phone wiring that is.
It could be quite possible that the other occupant was on the phone at the same time. This is a common issue in homes that were wired with quad wiring (no twists).
There are several ways to fix this. One way is to get new wiring. Another way is to plug the phone directly into the eMTA. A third way is to avoid talking on the phone at the same time as the other occupant.
The other occupant of the building does not have a home phone so that is out of the equation. I am wondering if I rewired the house with Cat 5 wire if that would take care of any interference. The modem is wired back to the demarc using the Halloween pair because the dial tone has to pass through the RJ31X before it hits the house phones, which is wired using the Christmas pair. It is connected to a piece of Cat 5 going to the RJ31X with Scotchlocks.
The interference sounds like radio transmissions coming from an illegal Ham radio setup.