Interior near-field acoustical holography in flight.
In this paper boundary element methods (BEM) are mated with near-field acoustical holography (NAH) in order to determine the normal velocity over a large area of a fuselage of a turboprop airplane from a measurement of the pressure (hologram) on a concentric surface in the interior of the aircraft. This work represents the first time NAH has been applied in situ, in-flight. The normal fuselage velocity was successfully reconstructed at the blade passage frequency (BPF) of the propeller and its first two harmonics. This reconstructed velocity reveals structure-borne and airborne sound-transmission paths from the engine to the interior space.
Williams
E G
EG
Naval Research Laboratory, Washington, DC 20375, USA. williams@genah.nrl.navy.mil
Houston
B H
BH
Herdic
P C
PC
Raveendra
S T
ST
Gardner
B
B
D000054:Acceleration; D000162:Acoustics; D000401:Aircraft; D006696:Holography; D006801:Humans; D013026:Space Flight