High-resolution remote acoustic localization of damage in vibrating plates

Abstract

Two major challenges exist for the remote acoustic localization of damage in vibrating structures. First, the presence of damage typically results in small acoustic changes that may become “drowned out” by the majority of the sound which remains unchanged. To mitigate this, a high-resolution beamformer can be used to better resolve the acoustic sources, including the small changes (i.e., damage). However, this elicits the second challenge; many popular high-resolution beamformers exhibit poor performance in the presence of coherent sources—exactly the type of sources provided by extended, vibrating structures like a plate. To address both challenges, the Spectral Estimation Method with Coherent Background Removal (SEMCBR) is introduced, enabling the localization of small acoustic changes in a distribution of coherent sources. SEMCBR is an extension of the existing Spectral Estimation Method with Additive Noise (SEMWAN), which has previously been applied to quantify incoherent aeroacoustic sources, combined with an additional subarray averaging step to suppress coherent cross-terms. Experimental results using SEMCBR are provided for the localization of cuts, fastener faults, and delamination in 30-×-30-×-0.16 cm plates base-excited from 100–6000 Hz, using an 8-×-8 array of remote receivers. [Sponsored by NAVSEA through the NEEC and by the US DoD through an NDSEG Fellowship.]Two major challenges exist for the remote acoustic localization of damage in vibrating structures. First, the presence of damage typically results in small acoustic changes that may become “drowned out” by the majority of the sound which remains unchanged. To mitigate this, a high-resolution beamformer can be used to better resolve the acoustic sources, including the small changes (i.e., damage). However, this elicits the second challenge; many popular high-resolution beamformers exhibit poor performance in the presence of coherent sources—exactly the type of sources provided by extended, vibrating structures like a plate. To address both challenges, the Spectral Estimation Method with Coherent Background Removal (SEMCBR) is introduced, enabling the localization of small acoustic changes in a distribution of coherent sources. SEMCBR is an extension of the existing Spectral Estimation Method with Additive Noise (SEMWAN), which has previously been applied to quantify incoherent aeroacoustic sources, combine...