Active Control of the Flow-Induced Noise Transmitted Through a Panel

Abstract

Active control of sound transmitted through an elastic panel when excited by a turbulent boundary layer is investigated. The motivation is the control within an aircraft cabin of the ow-induced noise due to the wallpressure uctuations over the fuselage. The excitation is random and so the plate velocity and the radiated sound pressure must be described by spectral densities. These quantities can be obtained from an analysis of the response of the system to a harmonic deterministic excitation and a statistical model for the turbulent boundary layer. Criteria are discussed under which the cross-modal coupling of the structural modes can be neglected when excited by a turbulent boundary layer. When considering subsonic turbulent ows, parametric studies show that each structural mode radiates sound independently. Hence, a suitable strategy for the active structural acoustic control of the sound power transmitted through the panel would be independent feedback control of each structural mode of the system in the low-frequency domain. The performance of this active control strategy is compared to that obtained by controlling the radiation modes of the panel for different numbers of control channels.

Controller Complexity for Active Control of Turbulent Boundary-Layer Noise from Panels

“…9 Loop shaping by observing the closed-loop performance on a Nichols chart was required, thus limiting the usefulness to the low-modal-density (frequency) region. The analytical work presented by Maury et al 6 agrees qualitatively well with the work presented in this paper.…”

“…Feedback control of TBL excited noise has been studied analytically 6 ; however, there has been little experimental work in this area. An analytical study of feedback control of sound radiation caused by TBL was described by Thomas and Nelson 7 and later studied in an experiment with a simulated TBL excitation.…”

Fourier Transform Sound Radiation

“…Alternatively, passive measures such as inserting fibrous sound absorptive materials in the partitioned cavity of sandwich structures may be a preferable choice to achieve a compromise between noise-reduction efficiency and financial cost. For instance, the fuselages of commercial aircrafts are commonly made of periodically rib-stiffened composite structures filled with fiberglass to enhance thermal and sound insulation [6][7][8][9]. This provides strong impetus for the development of effective theoretical models to predict the sound radiation characteristics of periodically rib-stiffened sandwich structures filled with sound absorptive materials.…”

“…Active control algorithms with sensors and actuators have been developed to reduce structural vibration and sound radiation [6], which however inevitably brings the penalty of increasing system complexity and financial costs. Alternatively, passive measures such as inserting fibrous sound absorptive materials in the partitioned cavity of sandwich structures may be a preferable choice to achieve a compromise between noise-reduction efficiency and financial cost.…”

Interaction Metrics for Feedback Control of Sound Radiation from Stiffened Panels

“…[1][2][3][4] Feedforward control is less common in this application due to the absence of a reference signal which is correlated with the TBL excitation. Numerous analytical studies have demonstrated the potential for feedback control on this problem.…”