An acoustically treated exhaust centerbody comprising a body including a body fore portion and a body aft portion. An internal passageway extends through the body in the axial direction. A resonator in the body fore portion includes a plurality of acoustic chambers. A plurality of ribs in the resonator form fore/aft walls of the acoustic chambers. Each rib is shaped substantially as a section of an annulus. A plurality of radial fins extend between adjacent ribs. The fins form sidewalls of the acoustic chambers. A skin overlies the acoustic chambers and forms an outer surface of the resonator.