Low-frequency measurements and predictions of the structural-acoustic properties of the INCE standard T-beam structure

This paper assembles and examines a collection of measurements and predictions of the low-frequency (< 1 kHz) structural-acoustic behavior of the INCE standard T-beam made by several investigators using different techniques, and in some cases, different hardware. The T-beam is one of a series of INCE standard test structures, which includes ribbed panels and flexible panels coupled to rigid walled enclosures. The assembled methods and data are examined to provide guidance regarding procedures for accurate measurements and modeling of connected beam structures. Modes, power input spectra, power dissipation in the legs of the T-beam, and structure-borne power through the legs are presented, all using consistent T-beam properties, for the first time. Finite element (beam and solid element models), analytic wave-based, and mobility power flow predictions compare very well to measurements made on two nominally identical T-beams. Some discrepancies between the various predictions and the measured data remain unresolved, however, and it appears that the key issue in predicting accurate structure-borne power flow behavior in connected beam structures is how best to represent the joints, which need to be modeled as finite sized connections between the legs. One of the key issues in making accurate structure-borne power measurements is careful alignment of the driving hardware (usually shakers) to the test structure to avoid inadvertently exciting resonances not of interest. Also, care must be taken to ensure precise phase calibration between sensors and to account for mass loading effects of shakers and other instrumentation hardware when comparing measured and predicted datasets.