Fix Crackling Static on Analog Phone Lines and Station Ports
Crackling type static on an analog phone line is caused by a bad connection (high resistance) or a short to foreign voltage / ground.
In the old days it was often caused by the open (un-insulated) telephone wires running between insulators on telephone poles swinging in a strong wind, occasionally touching a wire from another telephone line. That was called a "swinger."
A more serious problem that also caused static was when one of the telephone wires touched a power wire. The current from the power line going into the phone line can cause fires and serious bodily harm. It can still happen today.
You don't hear crackling static if you have a bad connection on the speaker wires from your stereo. That's because there is no DC on those wires. Only AC audio. When there is a bad connection or short on your speaker wires you hear the volume go down - no static.
If you're hearing static on an analog phone line or station port the cause of the problem has to be fixed, there is no filter for "static."
Some people call data noise, often picked up inductively from nearby computer equipment, static. There's a big difference in the crackling static caused by a bad connection or a short and data noise (which is more of a consistent hiss or humming sound).
If the problem is at the demarc with the inside wiring disconnected the phone company has to fix it. If the problem is inside you have to try a spare pair or replace the cable.
It's harder to fix an intermittent problem that might only happen in bad weather!