This paper has presented the concept of adding a single active 'tunable' dynamic mass to an aircraft panel to reduce the TBL (Turbulent Boundary Layer) generated sound power radiated into the aircraft interior. An approach to estimating the optimum dynamic mass was outlined, and it was shown that a simple secondorder oscillator approximation to that dynamic mass can provide comparable performance. The generation of a desired dynamic mass using an active control system was demonstrated in the laboratory using a mass as the structure and two shakers, one for the disturbance and one, equipped with a force gauge and accelerometer, for the active impedance. Good agreement between the desired dynamic mass and that achieved by the control system was shown. When the performance of the concept was estimated analytically using the measured accelerance on a test panel and the measured accelerance of a commercially available miniature piezoelectric actuator, the system did not effectively reduce the power radiated when the panel was excited by a TBL. The source of the problem was found to be that the dynamic characteristics of the actuator placed such severe demands on the control system, that it could not control the actuator to effectively match the desired dynamic mass. By designing the actuator to have a dynamic mass that was similar to, but not the same as, the desired dynamic mass it was shown that good performance could be restored. Finally the degree of adjustability of the dynamic mass of the actuator by the control system suggests that the controller has the potential to be able to adjust the characteristics of a properly designed actuator to deal with changes in operating conditions and panel to panel variations in an aircraft fuselage and provide significant reductions in radiated power near panel resonances over a fairly broad range of frequencies.
Reduction of turbulent boundary layer induced interior noise through active impedance control
Reduktion des von turbulenten Grenzschichten induzierten Innengeräusches durch aktive Impedanzregelung
Journal of the Acoustical Society of America ; 123 , 3 ; 1427-1438
2008
12 Seiten, 13 Bilder, 1 Tabelle, 24 Quellen
Article (Journal)
English
Boundary-layer-induced noise in interior of aircraft
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