Akustische Untersuchungen zur aktiven Reduktion der Schalltransmission von modernen CFK-Rumpfstrukturen bei Anregung durch eine turbulente Grenzschicht

Abstract

The growing use of light-weight structures in the aerospace but also in the automotive industry spotlights the challenging vibroacoustic properties and its implications on comfort and reliability. Aircraft noise mainly originates from the turbulent boundary layer (TBL) and the engines (jet or rotor noise). The TBL induces a broadband, stochastic vibration of the fuselage structure causing the noise transmission into the cabin. The concept of active structural-acoustic control (ASAC) facilitates a light-weight compliant improvement of transmission loss in the low-frequency range (< 500Hz). In this frequency range, passive noise abatement methods inevitably result in a signifi-cant increase of mass and volume. The radiation mode concept was adopted in order to integrate an acoustic performance metric into the control-design that purely relies on structural sensor in-formation. Its validity for different panel configurations (non-stiffened and stiffened) was experi-mentally investigated in the acoustic wind tunnel of DLR (TBL excitation). For reasons of numeri-cal efficiency the principal components of the radiation resistance matrix were interpolated by low-order digital filters. The predicted radiated sound power by this structurally-based technique has been compared to acoustic nearfield holography and sound intensity measurements.