Aircraft hardware in the acoustic loop : testing environment

Abstract

The development and design of acoustic noise reduction treatments in aviation are often based on numerous tests to parameterize the calculation models as well as to verify and validate them. While individual components can also be tested for their transmission and absorption properties using vibroacoustic methods on shakers, in acoustic windows, or in Kundt’s tubes, their overall acoustic performance when installed in the aircraft often shows significant differences in practice compared to isolated individual component measurements. This article presents a test-based implementation of creating an equivalent acoustic broadband random excitation outside an A320 fuselage section located in an acoustic climate chamber, which creates the same response spectrum inside the passenger cabin as in a real flight. This enables the installation and evaluation of developed acoustic treatments under realistic operating conditions in interaction with aircraft structures and components. In addition to investigating the direct influence of acoustic treatments in the mock-up, a concept for separating airborne and structureborne sound components in the transfer paths of the cabin by means of cross-correlation with realistic excitations is presented. The approach allows more accurate characterization of transfer paths and hence supports the design of more effective noise reduction solutions for future aircraft.