US Patent 11524792 Surface trim for acoustic absorption

A surface liner member includes an external wall which is provided with multiple holes, a spacer structure, and tubes which are respectively associated with the holes in the external wall. The surface liner member is intended to be applied to a base surface in order to reduce, by acoustic absorption, an acoustic wave reflected on this base surface. The acoustic absorption efficiency is improved, particularly for frequencies below 500 Hz, by varying the shape of the holes in the external wall such that the ratio of the hole perimeter to the hole area varies. Such a surface liner member may be adapted to form a surface portion of an aircraft engine nacelle, or of a leading edge of an aircraft wing.