An annular air baffle for use in a cavity of an annular rotatable gas turbine engine component includes an annular split baffle ring having a plurality of circumferentially spaced apart and radially inwardly extending intermediate dams circumferentially disposed between first and second end dams. A first side gear and a second side gear are substantially axially aligned and spaced apart from one other, each of the side gears being supported by the differential housing for relative rotation therebetween and being adapted to engage an axle half-shaft. An impeller is disposed in the chamber of the housing and is adapted to induce a flow to a fluid from the inlet to the first and second outlets. In addition, the disclosed calibration technique can be used even when multiple acoustic sources are present.