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By Mathias Winberg, Sven Johansson and Thomas Lagö


Abstract Different actuators have been developed for active noise control. A broadband linear actuator, typically a loudspeaker, is often used. However, this is not an absolute necessity, the important issue is that the performance is “good” in the frequency band where the actuator should work, and that the actuator can produce the volume displacement needed. A speaking panel is a lightweight actuator, intended to be applied in propeller aircraft where the weight consideration is of great importance. The dimension of the used speaking panel is 200x600 mm. The panel is based on piezo ceramic materials embedded in a thin carbon fiber plate, resulting in a lightweight and more flexible actuator for trim panel mounting in an aircraft, as compared to a normal loudspeaker. A disadvantage, though, is that the actuator shows a nonlinear behavior, that cannot be overlooked when designing the controller. The cabin noise inside a propeller driven aircraft consists essentially of tonal components originating from the propellers as well as broadband boundary layer noise. However, it is only the tonal components that will be targeted by the controller therefore a narrowband controller has been used in this application. With this in mind the nonlinear characteristics are evaluated in terms of frequency response functions and harmonic distortion. An evaluation of the speaking panels together with a MIMO complex filtered-X LMS algorithm, is presented. The setup consists of four speaking panels, mounted in a test mock-up, four control microphones and two monitor microphones. The controller is implemented on a Texas Instruments C31 signal processor

Topics: signal processing - active noise and vibration control, active noise control, actuator, speaking panels, harmonic distortion
Publisher: School of Engineering - Dept. of Signal Processing/Blekinge Institute of Technology
Year: 2005
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