Investigation of potential benefits and functionality of a vibroacoustic camera by combining results of a common beamforming and nearfield holography acoustic camera and a highspeed camera, allowing to visualize structural vibration (optical flow tracking

Abstract

In this paper potential benefits and functionality of a vibroacoustic camera are investigated by combining results of a common beamforming and nearfield holography acoustic camera using the software NoiseImage and a highspeed camera, allowing to visualize structural vibration (optical flow tracking) using the software WaveImage. Both results can be used to calculate color maps - mapped parameters are sound pressure, vibration displacement and its derivatives. The authors will investigate how the combination of methods might enhance understanding and interpretation of the vibroacoustic behavior of specimens in the overlapping frequency range. At low frequencies, the beamforming approach is limited due to main lobe width and array size. While the limits for source localization can be offset employing nearfield acoustic holography, those methods can be time consuming and might fail for complex 3-dimensional structures. It was also previously shown that mode shapes of 2-dimensional structures can be reproduced using nearfield acoustic holography (SONAH). The highspeed camera results present a way to provide positions of local vibration maxima and operating deflection shapes without accessing the acoustic nearfield. Accordingly, the approach could be viewed as a potential extension of the frequency range in which meaningful visualization of vibroacoustic data can be achieved from a single far field measurement from 0 Hz to the ultrasound frequency regime.