A cellular acoustic structure for a turbojet engine includes a closed wall. The closed wall includes at least two faces having acoustically transparent areas and acoustic reflective areas. The closed wall is filled with a plurality of cells, and the acoustic reflective areas are disposed within the closed wall so that an acoustic path of aerial sound vibrations travels through the acoustically transparent areas, penetrates inside the cells and reflects on the acoustic reflective areas. In particular, the acoustic path in some of the cells has a depth greater than a half of the thickness of the cellular acoustic structure.