Structural acoustics and active constrained layer damping (ACLD) of an aircraft fuselage section

Active structural acoustic control of an aircraft fuselage section is demonstrated using active constrained layer damping (ACLD), where both interior acoustic levels and surface vibrations are reduced. The uncontrolled response of the fuselage is evaluated under several different physical forcing functions by performing dense spatially sampled broadband (10–1000 Hz) measurements of surface velocity and interior pressure. One of these forcing functions is a point force applied to the stiffener skeletal structure. This response reveals rich structural acoustics, exciting broad wave numbers and local resonances, both of which excite the interior acoustics. This case is further investigated using a finite/infinite element model of the fuselage section and the interior/exterior fluid. Twelve ACLD patches are strategically positioned on the fuselage to target control of the offending modes. Each patch is constructed of a passive viscoelastic layer and an active piezo film; these patches are lightweight and inexpensive, which makes this technique practical in-flight and attractive to commercial industry. Good performance is achieved under a point force disturbance using simple minimization control laws. Reported are the structural acoustics that are observed from these high spatially sampled measurements along with the results of the control experiments. a)Also with SFA, Inc., Landover, MD.