Noise reducing attachment for a turbofan engine

The fence element has two posts connected by a transverse rail (3) supporting a number of vertical bars (5), the rail having U-shaped openings (31) that match the transverse cross-section of the bars formed by folding sheet metal. The bars can be partially engaged (F1) in the openings, and the bars each have a relief (54) that acts as a stop against movement of the bar into the rail. Independent claims are included for a fence for delimiting a space to be protected and a process for assembling a fence element.