Compliance frequency response function (FRF) data and model fit obtained from the ulna of a 54-yr-old female with a BMI of 22. The complex compliance FRF (red irregular line) and best model fit (black smooth line) demonstrate resonances at approximately 200 and 800 Hz. The location and shape of the higher frequency resonance are determined primarily by the mechanical properties of the skin and the applied static load (labeled “soft tissue peak” in the figure), while those of the lower frequency resonance are determined primarily by the mechanical properties of the underlying bone (labeled “bone peak” in the figure).^40,43 Both resonances are also affected by damping effects of surrounding soft tissue. There is notable non-biological low frequency (<50 Hz) noise that is attributed to the mechanical system. The model fits data between 70 and 1600 Hz; thus, the model is not influenced by this low-frequency noise. Sub-harmonic noise that is omnipresent at 1050 Hz has been removed for visual clarity, as this sub-harmonic is zeroed out and is not fit in the model. Ulnar flexural rigidity is ultimately quantified based on the compliance FRF model fit.