Transmissibility response analysis of a human body in semi-supine posture exposed to low-frequency vibrations

Abstract

The study presents transmissibility responses of 14 male subjects exposed to vertical sinusoidal vibration (2.0–16.0 Hz) at five vibration magnitudes (0.5–1.5 m s⁻² r.m.s.). The vibration magnitudes are measured at five body locations: head (at the forehead), sternum, abdomen, thigh, and leg, for which the transmissibility at each body location is statistically analyzed. The nonlinearity in the transmissibility response, that is, decrease in resonance frequency with an increase in vibration magnitude, is evident for the sternum, abdomen, thigh, and leg. The higher vibration magnitude causes greater segmental transmissibility at excitation frequency lower than the resonance frequency. The highest vibration transmissibility has been observed for the abdomen, followed by the thigh, sternum, and head. The findings indicate that the higher energy content associated with the sinusoidal waveform further softens the tissues in contact with the vibrating surface.

Practitioner Summary: The present study provides transmissibility responses of the semi-supine posture of humans at the head, sternum, abdomen, thigh, and leg under vertical sinusoidal excitation (2.0–16.0 Hz). Pronounced transmissibility is obtained for the abdomen among the other body segments, followed by the thigh, as both consist of a majority of soft tissues.