On the noise reduction of active sidewall aircraft panels using feedforward control with embedded systems

Kurzfassung

Keeping aircraft interior noise on an acceptable level is an important aspect for the passenger comfort and health in modern aircraft design. Generally there is a trade-off in the achievable transmission loss of aircraft and the additional weight of the insulation provision, especially at low frequencies below 500 Hz. In this frequency range, passive methods for sound insulation usually have high weight and volume requirements for suitable performance in aircraft. The present work focuses on aircraft with rotor engines having characteristic low frequency narrow banded noise sources due to the rotational speed of the rotors. A major transmission path of the noise is given by the linings of the aircraft cabin, which are coupled to the fuselage. These large sound emmitting surfaces radiate the noise directly into the passenger zone. Active control is a promising method to reduce at least the low-frequency noise radiated by the panels. These so-called smart linings, augmented with suitable actuators and sensors, are also usable for additional tasks, such as e.g. passenger announcements and noise masking. The feasibility of active feedforward control to reduce narrow banded frequencies below 500 Hz has already been tested successfully at DLR on test panels and in a fully equipped test aircraft on ground, which are excited externally by a loudspeaker array. This paper is dedicated to a discussion of the recent activities to simplify the underlying control strategies in a way that they can be implemented on small embedded systems with limited performance. In the future, such microprocessor units enable the integration of the actuators, sensors and control algorithms directly into smart lining modules, having a positive effect on maintainability and weight footprint of the smart Panels.