Assembly forming a sound-absorbing material

An assembly forming a sound-absorbing material, the assembly comprising:

• a sheet having at least two first zones pierced with holes and, for each first zone, a solid second zone, wherein the at least two first zones and the solid second zones are disposed alternating along a direction of alignment, and
• conduits, wherein for each of the at least two first zones and an associated second zone, a conduit having a first end bearing against the sheet proximate a first first zone of the at least two first zones and a second end which bears against the sheet around the associated second zone,
• said conduits stacked one on another in a first stacking direction perpendicular to the direction of alignment.