An assembly forming an acoustic insulator having a first sheet, a pierced second sheet, and a plurality of first and second structures. Each first structure comprises a first and a second strip, wherein each is shaped to form half of the wall of a cage and wherein, for two successive halves, each strip comprises a facet of a joining wall. Each second structure is made up of a first and a second strip, wherein each is shaped to form half of the wall of a cone, wherein. For each strip, at least one of the wall halves of each cone is pierced. For two successive halves, each strip comprises one facet of the connecting wall. Each cone is located in a cell and each connecting wall is located between the two facets of a joining wall, and, between two adjacent first structures, a second structure is likewise fitted.