Resonances in the apparent mass of the human body occur at lower frequencies when the vibration magnitude is increased – a non-linearity that has been found with seated and standing persons. Increased harmonic distortion has been found in the dynamic force at the seat and the acceleration of the spine and pelvis for seated subjects exposed to higher magnitudes of vertical sinusoidal excitations at the resonance frequency. An experiment has been performed to measure harmonic distortions in the dynamic force with 12 subjects lying in a relaxed supine posture during vertical sinusoidal vibration (i.e. in x-axis of the supine body) and longitudinal horizontal sinusoidal vibration (i.e. in z-axis) at nine frequencies from 2.5 to 16.0 Hz at two vibration magnitudes (0.25 and 1.0 ms-2 r.m.s.). With both vertical and longitudinal horizontal sinusoidal excitation, the distortions in the dynamic force were greater at greater vibration magnitude. Greatest distortion occurred around the frequency of the apparent mass resonance. The dependence of harmonic distortion on vibration frequency and vibration magnitude in the relaxed supine body appears similar to that in seated subjects.
|Publication status||Published - 2007|
|Event||The 42nd United Kingdom Group Meeting on Human Responses to Vibration - ISVR, University of Southampton, Southampton, England|
Duration: 17 Sept 2007 → 19 Sept 2007
|Conference||The 42nd United Kingdom Group Meeting on Human Responses to Vibration|
|City||ISVR, University of Southampton, Southampton, England|
|Period||17/09/07 → 19/09/07|