Embodiments of the invention are shown in the figures, where a nacelle cowling structure for a turbomachine having a bypass duct defining a path for an airflow is provided, the nacelle cowling structure including: an outer layer defining an external surface of the nacelle cowling structure, an inner layer defining a surface of the bypass duct, a front mounting area for fixation to the turbomachine and a rear mounting area for fixation to the turbomachine downstream the front mounting area with respect to the bypass duct flow path, wherein a space between the outer and inner layers and between the front and rear mounting areas is filled with acoustic material.