The invention pertains to an insulation structure for thermally and acoustically insulating an aircraft that features at least one heavy layer, wherein the insulation structure according to the invention is characterized in that the insulation structure comprises an additional absorption layer, in that the heavy layer is perforated at least in certain areas, and in that the perforated area ratio of the heavy layer is adapted in such a way that the heavy layer is essentially transparent to sound for frequencies below a double-wall frequency of the insulation structure. This makes it possible to dampen sound with low frequencies below the double-wall frequency as effectively as possible.