Abstract
An invisible microvibration (MV) is observed from body surface. Concerning the mechanism generating MV, it has been considered that MV is caused by cardiac activities and muscle tones and affected by the autonomic nervous system in a complicated way. However, its mechanism has not yet been made evident. This paper firstly proposed a vibration model of body to reveal the conduction mechanism of microvibration in a body. We gave a theoretical method to separate the vibration caused by cardiac activities (ballistocardiographic component) from the muscle tones (muscular component) and the other factors. Then it was shown that the ballistocardiographic component had nearly 70% of the whole MV power at the left shoulder, although the ratio somewhat depended on frequency. We also found the conduction time of ballistocardiographic component from the heart to the left thenar was approximately 0.13-0.16 seconds. Furthermore, we showed that the presented method in which ballistocardiographic vibration is analyzed on the prediction residual signals as well as on the power spectra by applying autoregressive model is useful to clarify its conduction properties.
