A400M Fuselage Controlled by Optimized Set of Tuned Vibration Absorbers

Propeller driven airplanes face the challenge of low frequency interior noise. In this case passive noise treatments promise generally less efficiency than active systems. Research on active control of aircraft noise and vibration over the last decades, mostly on simplified test objects, led to just a few practical applications on small aircraft. This paper presents the application of an active structural acoustic control system in the cargo hold of the large turboprop aircraft A400M. The system consists of 245 Tuneable Vibration Absorbers (TVA) and 490 microphones. The TVAs are spring-mass systems, which are driven by voice coils, and whose natural frequencies are adjusted to the blade passage frequencies of the propellers. There are signal processing devices on each TVA, and the TVAs are connected to the central control unit by CAN bus. An overview of the system features is presented together with a workflow for genetic optimization of the sensor and actuator positions. The experimental results show that a remarkable global noise reduction can be achieved. Suitable component setups of the system can be found by genetic optimization without a considerable loss of noise reduction. This is validated by experiments with reduced setups.