Three-dimensional laser Doppler vibrometry of the dry human skull.

Abstract

The results of an experimental study of the vibratory response of the dry human skull at acoustic frequencies (250 Hz–16 kHz) are presented. In three dry skulls, the motor from a clinical bone vibrator, the BAHA Divino, was used to excite vibrations, and the amplitude and phase of the response were measured with a Polytech PSV-300 scanning laser Doppler vibrometer. Data were acquired at 2200 points covering the entire skull surface at ∼5 mm resolution. The experiment followed a stepped-sine paradigm with excitation frequencies spaced linearly at 200 Hz. The experiments show that the dry skull undergoes quasi-rigid motion at low frequencies, which breaks up into modal vibration patterns above 1000 Hz. At frequencies above 8000 Hz, clear standing wave patterns can be seen with wavefronts radiating out from the excitation location. The data are consistent with the response being primarily plate-bending motion. Progress of reproducing the data with a finite element model will also be reported. Geometry for the model was acquired using a high-resolution CT scan imported into HyperMesh® and the simulation was performed in LS-DYNA® hydrocode. [Work supported by the Atlantic Canada Opportunity Agency’s (ACOA) Atlantic Innovation Fund and the Natural Sciences and Engineering Research Council (NSERC).]