A hybrid frequency-based/mode component synthesis model for cabin noise prediction with arbitrary damping distribution

Kurzfassung

The design of low-frequency noise control measures in aircraft cabins requires reliable and efficient calculation methods for interior noise. While computers are getting increasingly powerful, the iterative nature of the aircraft design calls for the ability to predict dynamic response of a huge amount of designs in a wide frequency range in a short time. Due to limited numerical resources, a lot of studies concentrate on the component mode synthesis. Uncoupled modes of the structural and acoustic part are calculated and coupled on the fluid-structural interface. This component mode synthesis is shown to produce accurate results for the interior pressure calculation. However, most studies are limited to the use of rigid-walled acoustic modes or the incorporation of a classic damping model. The acoustic damping distribution in an aircraft cabin is highly arbitrary and therefore the modes can become complex-valued. This paper aims at the introduction of a hybrid computation model, where the structural part is frequency-based and the acoustic cavity incorporates a subset of complex-valued modes. The hybrid computation model facilitates the calculation of many structural designs while leaving the acoustic eigenvectors unaltered. It is shown, that due to the frequency-based nature, the structural part converges with very few acoustic modes and the modal projection of the acoustic part leads to a significant reduction in computation time with only a slight accuracy loss in the considered frequency range.