Circles
When you print circles, or curves, the print may seem slow or it may make a strange sound. This is normal.
STLs have no curves. The entire thing is made up of triangles. Nothing but straight lines. When you export a curve it is converted to a bunch of triangles that look like a curve. The number of triangles used to simulate a curve can be set by some software. When you hear things like low polly it refers to there being a low number of triangles making up a curve and you may be able to see the straight lines in place of a smooth circle.
STEP files allow curves, but they do not require them. A STEP can have either a bunch of triangles simulating a curve or a curve.
Gcode has instructions to move the printhead in a curve. Not all printers support them.
Some slicers do not support curves and use straight lines to simulate them.
So, now you are printing a circle, but it is made up of a bunch of straight lines. At the start of each little line the velocity is 0 the head accelerates and decelerates so the velocity at the end of the line is O. The sound is the printer accelerating and decelerating for all the little lines as it goes around. The reason it is slow is that it is drawing all those short lines and never gets up to speed.