Low-frequency acoustic center body

A center plug for attenuating noise in a gas turbine engine, comprising:

• an inner skin, the inner skin having a substantially cylindrical shape and extending along an axial centerline;
• an outer skin positioned radially outside the inner skin;
• a forward bulkhead disposed proximate a forward end of the inner skin, the forward bulkhead connected to and extending radially outward from the inner skin;
• an aft bulkhead disposed proximate an aft end of the inner skin, the aft bulkhead connected to and extending radially outward from the inner skin;
• and
• an acoustic panel disposed within a volume defined by the inner skin, the outer skin and the forward bulkhead and the aft bulkhead, the acoustic panel including
• a resonator cavity comprised of a plurality of sub-cavities extending axially along the axial centerline and circumferentially about the axial centerline, the plurality of sub-cavities including a first sub-cavity and a second sub-cavity, the first sub-cavity being separated by the second sub-cavity in a circumferential direction by a first perforated wall,
• a first perforated surface extending in an axial direction and through the outer skin and into the first sub-cavity,
• a non-perforated surface covering the second sub-cavity and
• a second perforated surface extending in the axial direction and spaced in the circumferential direction from the first perforated surface by the non-perforated surface.