I too hear the rhythmic knocking on wood when on a cell phone call.
It is not static. It is not clicking. I hear it when I'm talking regularly with the phone to my ear, on speaker, and on Bluetooth hearing aids. I get it talking to a different area code. I use T-Mobile. I get it talking via my iPhone SE 2022 to a Galaxy Android. I can hang up and call again and the problem will stop but may crank up again on that new call.
It seems to me to be a network problem. Only I can hear it and not the other party.
Weird that it sounds just like someone rapping/tapping on a wooden table.
Good luck with it.
If I can help you (Apple) in any way to investigate I will.