Transmissibility of supine human body exposed to tri-axial unidirectional whole-body vibration

This experimental study aimed to explore the effect of vibration magnitude and direction on the transmissibilities to different locations of the body in a supine posture. The transmissibilities to the head and chest of a group of 12 male subjects were measured using single-axis random vibrations (0.25-20 Hz) in the fore-and-aft, lateral, and vertical directions at four magnitudes (0.2, 0.4, 0.6, and 0.8 m/s² r.m.s.). It was revealed that the resonance frequency in the transmissibility to each location of the human body was similar at approximately 4 Hz in the fore-and-aft direction and at about 2.4 Hz in the lateral direction. However, the resonance frequency in the transmissibility to each body location was found different in the vertical direction. The results also showed that the nonlinear characteristics of various parts of the supine human body are the most obvious under the fore-and-aft excitation.