Laboratory for Dynamics of Machines and Structures 
On the estimation of structural admittances from acoustic measurement using a dynamic substructuring approach
 D. Ocepek, M. Kodrič, G. Čepon and M. Boltežar
Applied Acoustics, 2021

download pdf   https://doi.org/10.1016/j.apacoust.2021.108115
Abstract
A reconstructed displacement field using near-field acoustic holography (NAH) serves as an alternative to conventional measurement methods when it comes to obtaining the high-resolution vibration response of a structure. The method is highly applicable as it enables direct, non-contact measurement of the 3D structural response based on a single acoustic measurement. Although useful, the method’s ill-posed nature limits its use in the field of structural dynamics. This problem can be effectively addressed by using regularization and/or field-separation techniques that can attenuate the noise and the presence of external acoustic sources. All these methods rely on the measurement of acoustic quantities; therefore, the reconstruction of structural admittances is based solely on the evaluation of the hologram(s). This article proposes an alternative approach to improving the accuracy of NAH-based structural admittances by integrating them with a few discrete response measurement on the structure itself. The formulation relies on the mixing of the high-resolution NAH measurement with accurate discrete measurements (e.g., accelerometer or laser vibrometer) using dynamic substructuring techniques. The proposed hybrid approach is a very powerful modeling methodology that can integrate high-resolution spatial measurements using NAH with the accuracy and consistency provided by precise translation discrete measurements. In order to mix two experimental response models System Equivalent Model Mixing (SEMM) method is proposed. An experimental case study on a T-shaped structure demonstrates the robustness and improved accuracy of the estimated structural admittances compared to the plain NAH formulation.
Authors

Researcher

Domen Ocepek, PhD Student

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  domen.ocepek@fs.uni-lj.si
  +386 1 4771 229

Assistant

Miha Kodrič, PhD Student

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  miha.kodric@fs.uni-lj.si
  +386 1 4771 614

Associate Professor

Gregor Čepon, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  gregor.cepon@fs.uni-lj.si
  +386 1 4771 229
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Professor

Miha Boltežar, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  miha.boltezar@fs.uni-lj.si
  +386 1 4771 608
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