C. Maury and T. Bravo
Forum Acusticum 2023
Del 11 al 15 de septiembre de 2023, Torino, Italy.
Micro-perforated liners can be of interest for the attenuation of the low-frequency noise in ducted geometries that can appear for instance due to the presence of a Turbulent Boundary Layer (TBL) excitation that contributes to the noise between 500 Hz and 2 kHz. Classical acoustic liners are locally-reacting devices constituted of perforates rigidlybacked by a honeycomb filled cavity. An alternative approach for reducing wall-friction in aero-acoustic applications is the use of facesheets with sub-millimetric diameter perforations. In this study, we perform a costefficient experimental characterization for comparing the performance of micro-perforated partitions with those of fibrous non-resonant absorbers for the attenuation of acoustic waves and flow-induced noise in a low-speed wind tunnel. Two types of excitations have been studied, a fullydeveloped TBL and a source-induced noise using flushmounted compression drivers. We have used a nosecone microphone system for the determination of velocity and intensity profiles above the micro-perforated and fibrous test sections. The results obtained showed that the sound pressure levels and intensity fluxes in the proximity of the wall-treatments present important modifications when considering micro-perforated panels at the cavity resonance.
