Sound holes

Sound holes

perforations in the wooden shutters of the belfry windows in church towers, for the emission of the sound of the bells. In early times they were simply horizontal divisions obtained by the arrangement of the planks. Afterwards the perforations were ornamental in character, shaped like a trefoil or quatrefoil, and harmonized with the character of the structure.

Fuente: Cyclopedia of Biblical, Theological and Ecclesiastical Literature