2pBV7. A modal characterization of the ovine head.

Session: Tuesday Afternoon, May 14

Time: 3:00

Author: Teresa A. Whitman
Author: Mark T. Morgan
Location: School of Agricultural and Biological Eng., Purdue Univ., West Lafayette, IN 47907-1146
Author: George R. Wodicka
Location: Purdue Univ., West Lafayette, IN 47907-1285


Although the vibrational response of the head has been observed to correlate with intracranial pressure when measurements are made directly on the skull [M. Stevanovic et al., Ann. Biomed. Eng. 23, 720--727 (1995)], the effect of the extracranial tissues of an intact head has only been hypothesized. In this study, the modal characteristics of the freely vibrating ovine head under various stages of intra- and extracranial tissue removal were determined. Frequency responses from 20 to 2000 Hz were measured using an accelerometer and impact hammer at 32 sites on 5 intact ovine heads, and after progressive removal of the jaw, intra- and extracranial tissues, and finally on the boiled and dried skull. Intra- and extracranial tissues increased modal damping and decreased natural frequencies. Dried skulls exhibited as many as 5 lightly damped resonances with the lowest occurring around 1 kHz, whereas only 2 heavily damped resonances were evident prior to boiling. The first resonance for the heads at various stages of tissue removal occurred between 200 and 400 Hz and similar mode shapes between heads were found at this lowest resonance as compared by the Modal Assurance Criterion. As natural frequencies increased, the modes became more complex, resulting in dissimilar mode shapes between heads. [Work supported by NSF.]

from ASA 131st Meeting, Indianapolis, May 1996