Physical basis of ballistocardiography. IV. The relative movement of subject and ballistocardiograph

Abstract

Amplitude characteristics have been calculated numerically from formulas derived in this paper for the low-frequency bcg (Gordon, Henderson, Burger), the middle-frequency bcg (Nickerson), and the high-frequency bcg's (Starr and Dock), taking the difference in movement of subject and bcg into account. In a few cases corresponding phase characteristics have been calculated. Two constants of the system were determined experimentally.

From this it appears that it is only the low-frequency bcg that gives ballistocardiograms that are distorted slightly. Moreover, the velocity and the acceleration can be recorded with an analogously slight distortion.