Systems and methods for reducing noise in aircraft fuselages and other structures

A method of manufacturing a structural assembly with a damping system for noise reduction, the method comprising:

• attaching a first stiffener portion of a stiffener to a skin, the stiffener having a second stiffener portion offset from the skin, the second stiffener portion having a first width;
• attaching strip of auxetic core to the second stiffener portion, wherein the auxetic core includes a honeycomb material that expands in a first direction when stretched in a second direction perpendicular to the first direction, the strip of auxetic core having a second width that is at least approximately the same as the first width, the strip of auxetic core further having a first surface facing at least approximately toward the stiffener and a second surface facing at least approximately away from the stiffener;
• covering at least a portion of the second surface of the auxetic core with a damping layer;
• and
• attaching a constraining layer to the auxetic core by sandwiching the damping layer between the second surface of auxetic core and the constraining layer.

A method of reducing noise in a structure, the structure including an aircraft skin and an elongate structural member, the elongate structural member having a cap portion offset from a base portion, the cap portion having a first width, the method comprising:

• attaching a base portion of an elongate structural member to a portion of an aircraft skin, the elongate structural member further including a cap portion spaced apart from the skin:
• attaching a strip of auxetic core to the cap portion of the elongate structural member, the strip of auxetic core having a second width that is at least approximately the same as the first width of the cap portion;
• covering at least a portion of the auxetic core with a damping layer;
• and
• attaching a constraining layer to the auxetic core by sandwiching the damping layer between the auxetic core and the constraining layer.