A double degree acoustic attenuation sandwich panel having a plurality of stacked components adhered together to form a unitary sandwich structure. The structure comprising an impervious facing of thin sheet material, a first honeycomb core with end wise directed cells, a first perforate facing of thin sheet material, a first thin layer of porous fibrous material, a second honeycomb core with end wise directed cells, a second perforate facing of thin sheet material and a second layer of porous fibrous material. The resulting sandwich panel has a predetermined flow through resistance between the outer surface of the first and second layers of porous fibrous material and the cells of the first and second honeycomb cores. The cell of the first and second honeycomb cores may be of equal or different volume cells and may be constructed of similar or dissimilar materials.