Vibratory properties and resonances of the isolated human ulna

The frequency response, at various points along the length and circumference, of two isolated human ulnas has been recorded during white noise excitation under 'free-free' conditions. Both bones showed a similar pattern of multiple frequencies of resonance; two fundamental mode resonances occurring in directions mutually at right angles. Further resonances appeared at higher frequencies, both in the same planes as the fundamental modes and in a second plane at 45 degrees; changing the plane of excitation through 90 degrees produced only small changes in the pattern of resonances. Both bones showed marked coupling between neighbouring resonances, with pulling of the frequencies of resonance so that the frequency of the resonant peak may appear to vary by up to 10%.