Molding element for manufacturing a noise reducing tread

A molding element for a mold used for manufacturing a tread of a tire having a plurality of contacting element delimited by a plurality of grooves, the molding element having a molding surface for forming a contact face of the contacting elements intended to come into contact with ground during rolling and a groove forming rib portion for forming the groove comprising two opposed rib side faces for forming two opposed groove side faces and a rib top face connecting two rib side faces for forming a groove bottom, the groove forming rib portion providing a space opening to at least one of the rib side faces and/or to the rib top face and an insert received in the space for forming a portion of the groove and a closing device in the groove, wherein the insert comprises a plurality of separately formed plates, at least one of said plates being a notched plate of thickness t1, and the notched plate includes at least one notch extending through a full thickness of the notched plate for forming a flexible fence of the closing device, the flexible fence having approximately the thickness t1.