Back when we had hardwired phones, we could hear the welder during alum TIG. On the old phones (the kind that had hold and line selection functions on the bottom), We just had to have the annoyance of listening to it. When we upgraded to a phone system, it would drop the calls.

We tried everything we could think of like moving the welder to the other side of the shop. Un rolling the ground lead (~50 ft) so as not to have the big electro magnet hanging on the wall. Nothing helped.

It may be nice to note - this was only on Aluminium (A/C setting). TIG of steel or stick welding never was noticed. Also, this was clearly radiated as the original phone system was not connected to line power. Also the fact that we could listen to it may give an idea to frequency?