MSI DFAT STUDIES
Comparisons of the Structural Response of a Test Article Excited by DFAT™
Diffuse and Non-Diffuse Acoustic Fields
by Marcos A. Underwood, PhD
Tu’tuli Enterprises and MSI DFAT Chief Scientist
This paper discusses the results from Direct Field Acoustic Tests (DFAT™) performed at MSI DFAT to evaluate how effectively nearly diffuse (low coherence) and non-diffuse (high coherence) acoustic fields, using MIMO andMISO control, excite the structural resonances of a test article. The criteria used is to compare the frequency of resonances excited by the resulting acoustic fields to what Modal Analysis predicts the modes of vibration, their natural frequencies, and damping to be. Test results from using the various acoustic fields created by DFAT™ to excite the test article (test panel), in the form of PSDs obtained from accelerometers mounted on the test panel are analyzed. This analysis is used to determine the relative ability of the various acoustic fields to properly excite test articles by examining how well the resonances shown by the PSDs match the damped resonant frequencies predicted by Modal Analysis.