[1] Lehigh Univ, Dept Mech Engn, Bethlehem, PA 18015 USA
[2] Virginia Polytech Inst & State Univ, Kevin T Crofton Dept Aerosp & Ocean Engn, Blacksburg, VA 24061 USA
[3] German Aerosp Ctr DLR, Inst Electrified Aero Engines, D-03046 Cottbus, Germany
[4] Brandenburg Univ Technol Cottbus Senftenberg, Tech Acoust Grp, D-03046 Cottbus, Germany