Abstract: A folded structure (and a blank of sheet material) capable of being folded to said structure is provided which structure is an acoustic horn comprising an acoustic horn comprising a tapered structure having a base end and an apex end, the tapered structure being formed from a sheet of foldable material, and comprising a wall member having a plurality of fold lines defining the edges of a plurality of juxtaposed panels, characterised in that at least two of the fold lines (73, 74) are arcuate to form a non-planar panel (55) bound by said arcuate fold lines both base end (51) and apex end (52) being open. The structure provides an inexpensive party product which can easily be shaped in flat form but provides pleasing acoustical properties.