Conceptual Design and Validation of a Bent-Perforation-Path Acoustic Liner

An acoustic liner concept is developed that increases the effective thickness of perforate sheet
holes by bending the perforation paths within the facesheet. This significantly increases both the
viscous-loss resistance and mass reactance properties of the acoustic liner, creating low-frequency
absorption utilizing a small amount of liner volume. An initial concept is designed, 3D-printed,
and tested in a normal-incidence impedance tube to verify the acoustic properties. Comparisons
to an impedance model are shown with good agreement to test data, although further work needs
to be done to more accurately capture the losses associated with bends within the hole. Follow-on
concepts are also discussed that attempt to address the current shortcomings of the initial design.