The paper presents a new method for vibration testing of articles such assatellites, aerospace subsystems, transportation subsystems, civil structures, or articleswhose reliability in operation may be evaluated using either mechanical or acousticvibration testing. The method can be used for direct field or reverberant acoustic testfacility testing (acoustic) systems or multiple-exciter (mechanical) testing systems toperform vibration testing. The method improves the ability of Multiple-Input-Multiple-Output (MIMO) acoustic testing systems to create diffuse or other types of acoustic fieldsand MIMO mechanical testing systems to produce vibration responses conforming to aninitial reference Spectral Density Matrix (SDM) specification in the least mean-squareerror (LMSE) sense. It provides an updated positive definite or semi-definite referenceSDM that enables such tests to run with less error, using minimum required drive power,as a function of the initial definition of the reference SDM, by modifying its coherenceand phase off-diagonal terms, to approximate initially defined off-diagonal terms in theLMSE sense, but maintaining its initially defined diagonal terms exactly, while accountingfor physical limitations existing in the overall MIMO testing system.
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