mechanical vibration characterization

Mechanical vibration characterization of radiating plates using laser Doppler vibrometry (LDV) for transducer validation.

Single-point laser Doppler vibrometer measurement setup for radiating plate vibration characterization
Single-point LDV measurement setup for mechanical vibration characterization of the radiating plate.

Mechanical vibration characterization

Using MATLAB-based automated control, single-point LDV measurements were performed to obtain not only the frequency response of the radiating plate but also its experimental modal analysis (EMA). The experimental results were compared with FEM simulations, and the underlying mechanism of the previously unreported combination resonance in stepped plate parametric array loudspeakers was first identified (Kim et al., 2025).

Experimental Setup
  • MATLAB-based automated measurement program
  • Spectrum analyzer, single-point laser Doppler vibrometer, power amplifier, stage controller, linear stages
Technical Skills
  • Orchestrated the spectrum analyzer, laser Doppler vibrometer, power amplifier, and stage controller from a single MATLAB program, so that once the setup had been aligned an entire modal scan ran to completion unattended.
  • Removed operator action between grid points, holding the excitation and acquisition settings identical across the whole scan so that the measured mode shapes could be compared against FEM predictions on equal terms.
FEM-predicted experimental modal analysis amplitude at 8th eigenmode
Experimentally measured modal analysis amplitude at 8th eigenmode
FEM-predicted modal analysis phase at 8th eigenmode
Experimentally measured modal analysis phase at 8th eigenmode
EMA of the radiating plate around the 8th eigenmode frequency. Amplitude: FEM (1st) and experiment (2nd). Phase: FEM (3rd) and experiment (4th).

The EMA of the radiating plate around the 8th eigenmode frequency showed close agreement between FEM predictions and experimental measurements, validating the accuracy of the modeling approach.

Velocity frequency response measurement setup of locally resonant metamaterial unit
Velocity frequency response measurement setup of the locally resonant metamaterial unit.
FEM and experimental velocity frequency response comparison for locally resonant metamaterial
The bold solid lines represent FEM predictions, while the translucent solid lines correspond to the experimental measurements.

Locally Resonant Metamaterial Characterization

To estimate the effective properties of a 3D-printed locally resonant metamaterial (LRM) and use the identified values to redesign it to meet the required resonant behavior.(Kim† et al., 2026)

Experimental Setup
  • Spectrum analyzer, single-point laser Doppler vibrometer, power amplifier, vibration exciter
Plate impedance measurement setup for radiating plate with and without locally resonant metamaterial
Plate impedance measurement setup for vibration-based characterization of the radiating plate with/without the locally resonant metamaterial.
Impedance response of radiating plate without and with locally resonant metamaterial
Impedance response of the radiating plate: without (gray) and with (blue) the locally resonant metamaterial.

Plate Impedance Characterization

Plate impedance characterization was performed to evaluate the frequency-dependent dynamic behavior of the radiating plate with and without the locally resonant metamaterial.(Kim† et al., 2026)

Experimental Setup
  • Spectrum analyzer, power amplifier, vibration exciter, impedance head, custom jig (Carefully designed to ensure rigid support while minimizing any influence on the measurement results.)
Miniature polymer diaphragm compliance measurement setup using passive excitation
Diaphragm compliance measurement setup.

Miniature Diaphragm Characterization

Because the compliance of thin and tiny polymer diaphragms (micrometer thick and sub-millimeter diameter) critically determines acoustic sensor performance, a precise measurement methodology based on passive excitation was established. Diaphragm compliance data were obtained and the methodology was validated by comparing measurement results with FEM simulations.

Experimental Setup
  • LabVIEW-based automated measurement program
  • Note that constructing a pressure chamber for controlled passive excitation would further improve measurement reliability and remains as future work.
Polymer square diaphragm under test and compliance measurement results
Polymer square diaphragm as the device under test (left), and compliance measurement result (right).

Related works

2026

  1. Nat. Commun.
    Dual-domain metamaterials co-integrated with a compact ultrasonic transducer for highly directional audio generation

2025

  1. J. Acoust. Soc. Am.
    Design, Analysis, and Experimental Validation of a Stepped Plate Parametric Array Loudspeaker
    Design, Analysis, and Experimental Validation of a Stepped Plate Parametric Array Loudspeaker
    Woongji Kim, Beomseok Oh, Chayeong Kim, and Wonkyu Moon*
    The Journal of the Acoustical Society of America, Sep 2025
    DOI Related
    Project

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