2016 tormach pcnc 1100 - strange sound circle mill arcs

I just bought a 2016 TORMACH PCNC 1100, and while running a simple engraving program, doing just the “ARCs” it would start making a strange swirling sound, and when the arcs were done the strange sounds would stop. I found it curious because while machining and angled line, using both axis X & Y it sounded normal. Does anyone have an idea of what this could be? Any help would be appreciated, thanks !

If you pull the tool out of the spindle and cut air do you still get the noise? My first thought is the song of the stepper motors but I wouldn’t think of that as a swirling sound.

This is happening while cutting air and light engraving, same sound.

If your machine is running pathpilot then , while cutting air, you can slow down the spindle then the feed rate to see if this noise is tied to either.