Control of aircraft interior broadband noise with foam-PVDF smart skin

A foam-PVDF smart skin design for aircraft interior noise control is discussed. The smart skin is designed to reduce sound by the action of the passive absorption of an acoustic foam (which is effective at higher frequencies) and the active input of a PVDF element driven by an oscillating electrical input (which is effective at lower frequencies). For performance testing, the foam-PVDF smart skin is mounted in the cockpit of a Cessna Citation III fuselage. The fuselage crown panels are excited with a speaker located on the outside of the cockpit and driven by a band-limited random excitation. A MIMO feedforward Filtered-x LMS controller is implemented to minimize the error sensor signals provided by microphones in the close proximity of the smart skin elements. Three different reference signals are implemented for the feedforward controller and are compared in terms of the interior noise attenuation achieved. The voltage sent to the disturbance speaker provides an optimal reference signal which is not realistic in practice. Therefore, the use of either a structural sensor (accelerometer directly mounted on the fuselage) or an acoustic sensor (microphone located close to the fuselage) is investigated to supply a practical reference signal. The potential of the smart foam-PVDF skin for reducing interior noise is demonstrated. (C) 1999 Academic Press.