High-resolution vibro-acoustic measurement and analysis of the DLR ISTAR aircraft to assess engine-induced cabin noise

Abstract

Aircraft engines, especially when mounted directly to the fuselage, inject a considerable amount of tonal vibrations into the airframe causing audible and comfort reducing cabin noise. Reducing this noise requires the development of specialised noise reduction systems. This is a time consuming and expensive endeavour. To speed up and ease this process a sufficiently detailed numerical model of the aircraft structure and the force injected by the engines is required. The DLR ISTAR, a Dassault Falcon 2000, was used for an extensive vibration measurement campaign. The goal of this campaign was twofold: Getting spatially dense information about the aircrafts vibro-acoustic behaviour to later update a finite element model for calculations in the mid-frequency range and to analyse the vibration injected by running engines into the fuselage structure. The measurements include the vibrational response to both shaker excitation and engine vibration of the DLR ISTAR at about 1400 positions acquired by a rowing grid of sensors. The results are presented in the form of operational deflection shapes and energy transfer paths calculated using structural intensity analysis.