Limitations in Predicting Human Vibration Response Characteristics From Manikins and Rigid Body Masses

The objective of this study was to use the driving-point impedance and transmissibility techniques to evaluate and compare the resonance behavior of two male humans, the Hybrid III aerospace manikin, and a rigid body mass using a rigid seat and a selected helicopter seat cushion. All occupants represented the 95th percentile or higher of the male population for weight. The results showed that the resonance frequencies associated with the peak impedance, chest, and head transmissibilities were significantly higher in the manikin regardless of the seating configuration or input acceleration level. While the magnitude of the peak impedance was higher in the manikin, differences in the chest and head transmissibilities depended on both the seating configuration and acceleration level. Neither the manikin nor the rigid body were effective in predicting the primary human resonance effects occurring in the sensitive region of 4 to 8 Hz. However, some similarity did exist when comparing the manikin response to human spine transmissibility data. A discussion of an alternative method for predicting human body resonances using mathematical models is included in this paper.