Experimental estimation of the sound power radiated from panels excited by a turbulent boundary layer

Abstract

This study addresses the experimental estimation of the radiated sound power from a panel excited by a homogeneous and fully developed turbulent boundary layer. Two approaches are investigated, one based on vibration measurements and the other on near-field sound pressure measurements. The first method estimates the radiated sound power from the vibration cross-spectral density matrix measured for a regular grid on the panel and the theoretical radiation resistance matrix. To reduce the number of sensors on the panel, a formulation is proposed to estimate the vibration cross-spectral density between two points not measured simultaneously, using additional reference sensors. The second method estimates the radiated sound power from measuring the near-field sound pressure. The far-field sound pressure is extrapolated from the near-field measurements using the Planar Nearfield Acoustical Holography principle. The radiated sound power is then deduced from the far-field pressure. The two methods are first studied numerically to verify their validity and to highlight their limits before being evaluated experimentally in an anechoic wind tunnel.