The longer the prints the more frequent the sound becomes.
I had the same thing and here's what I found on mine. It was the 'spiral plastic wrap' that the wires from the print head to the extruder motor are wrap in. When it goes in a long Y direction it compress the plastic and because of the way it's made will snap apart at the slits and make the popping sound. It may snap at one slit or several making several popping noises. It will do the same thing going back in the Y direction when it decompresses. The way I found this is just put your hand around the plastic while it's printing and you will feel the snapping. The way I fix it was just do nothing. The plastic eventually conformed to the curve it's in now and the noise went away.....that was my issue anyway..hope this might help....
I have the same issue.. it is annoying, but havent been able to fix it. There has been discussion about this in the google groups:
https://groups.google.com/forum/?pli=1# ... 8dzqZZo-cJ
Basically this is what Chuck said:
"Sometimes the belts will make a "popping" sound if they are mis-aligned, It's basically the belt riding up the side of the pulley and popping back into place.
It will make a regular ticking noise. Berend made a handy tool for this:
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