Application of feedforward and feedback structural control for aircraft cabin noise reduction

Abstract

The use of feedback and adaptive feedforward control within the Active Structural Acoustic Control (ASAC) framework is applied to the problem of propeller induced noise and vibration reduction in the passenger cabin of the de Havilland Dash-8 aircraft. Piezoceramic elements are used for structural actuation and either vibration or acoustic sensing is employed. Actuators comprised of segmented piezoelectric elements are designed with the objective of reducing the noise and vibration levels at the propeller Blade Passage Frequency (BPF) and the first harmonic. The actuator design objective was suppression of the operating deflection shapes (ODS) of the fuselage at the various frequencies by the judicious placement of piezoelectric elements. Using an identical actuator and sensor design optimized for the BPF, the feedback and feedforward controllers are found to yield similar results in vibration attenuation for the case of vibration sensing. The correlation in noise reduction is weaker between the two cases, although noise reduction performance is very good in both cases. At other frequencies, similar optimized designs for actuator and sensors are also found to exist, providing good noise and vibration attenuation. However, the advantage of acoustic over vibration sensing for noise reduction is clear when a