Sound absorbing devices for panels with openings

A sound absorbing device comprising:

• a panel with a first surface, a second surface, and an opening extending through the first surface and the second surface;
• a duct comprising a polyhedron shaped duct with planar sides with planar sides extending from the panel, the duct complimentary in shape, centered on, and being in fluid communication with the opening such that gas flows through the duct towards and through the opening;
• and
• a plurality of straight quarter-wavelength tubes arranged around and extending from each planar side of the duct and in fluid communication with the duct and embedded within the panel between the first surface and the second surface, the plurality of straight quarter-wavelength tubes extending entirely and parallel to along a single plane between the first surface and the second surface that is perpendicular to a length direction of the duct.

A sound absorbing device comprising:

• a panel with a first surface, a second surface, and an opening extending through the first surface and the second surface;
• a duct having a rectangular cuboid shape and extending from the panel, the duct complimentary in shape, centered on, and being in fluid communication with the opening such that gas flows through the duct towards and through the opening;
• and
• a plurality of straight quarter-wavelength tubes arranged around and extending from each planar side of the duct and in fluid communication with the duct and embedded within the panel between the first surface and the second surface, the plurality of straight quarter-wavelength tubes extending entirely along and parallel to a single plane that is perpendicular to a length direction of the duct, wherein the plurality of straight quarter-wavelength tubes comprises a first subset of straight quarter-wavelength tubes extending in a direction generally normal to a first planar side of the duct, a second subset of straight quarter-wavelength tubes extending in a direction generally normal to a second planar side of the duct, a third subset of straight quarter-wavelength tubes extending in a direction generally normal to a third planar side of the duct, and a fourth subset of straight quarter-wavelength tubes extending in a direction generally normal to a fourth planar side of the duct.