Development of an innovative noise generation system for turboprop aircraft fuselage testing

Abstract

This paper presents the development of a cabin noise testing equipment that will be used to evaluate the interior noise of regional aircraft as well as to aid the development of noise reduction techniques. The innovative noise generation system consists of three loudspeaker arrays positioned around the fuselage circumference to synthesize a pressure field that is similar to the pressure field seen by the fuselage during a flight. The acoustic pressure field generated by the loudspeakers is measured by a number of microphones scattered on the fuselage surface. These microphone signals are then fed back to the controller with the purpose of minimising the error between the target pressure field and the measured one by means of an iterative learning approach. The number and location of the microphones used in the control loop are selected through a pre-test optimisation analysis, which aims to reduce the time and cost of the set-up. A small-scale electroacoustic demonstrator has been built to develop the feedback control approach. A frequency domain multi-input multi-output feedback controller is used to replicate the random pressure field generated by the turbulent boundary layer excitation. The multi-harmonics of the propeller induced excitation are then added to the time histories of the broadband noise using a time waveform replication technique. Different arrangements of the driving signal distribution are investigated, and the results are then presented in terms of accuracy of the pressure field reproduction.

Multiple-Input Multiple-Output Acoustic Testing of Turboprop Fuselage Structures

“…Once the reference time traces have been generated using Simcenter ROTOR, the TWR algorithm can be applied during a test as described in [10]. Fig.…”

“…This paper presents an innovative noise generation system (iNGS), object of CONCERTO project (GA 886836), that tries to address these limitations using three rings of loudspeaker arrays that cover the full fuselage section, a multiple-input multiple-output (MIMO) closedloop controller for the automatic tuning of the loudspeakers, and the simultaneous replication of both the TBL noise and the blade passage noise. This work builds on previous research [10][11] and it focuses on the validation of the proposed approach on a full-scale iNGS. The design and the realization of the iNGS mechanical structure are illustrated in Sect.…”