Definition of a range of idealized values to characterize seated body biodynamic response under vertical vibration

While a considerable quantity of data has been published on driving-point mechanical impedance, apparent mass and seat-to-head transmissibility magnitude and phase characteristics of seated subjects under vertical whole-body vibration, significant variation is known to exist between various data sets. Such variations may be partly attributed to differences associated with the methodology, experimental conditions or subject population used by various investigators to determine the biodynamic response characteristcs. As part of this study, various published data sets on driving-point mechanical impedance, apparent mass and seat-to-head transmissibility are identified for which the experimental conditions are reported to fall within a prescribed range of conditions for subjects maintaining an erect seated posture without backrest support, while the feet are supported on a vibrating platform. Only those data sets are considered for which the magnitude of vertical sine and/or random excitation is reported to have been maintained below 5m s(-2). A further screening of the data sets defining the magnitude and phase responses of each function is performed by eliminating all data representing outliers in the 0.5-20 Hz frequency range. On that basis, mean and envelopes of the magnitude and phase responses associated with each function are derived in the 0.5-20 Hz frequency range, representing the most probable values likely applicable under the predefined range of conditions. The resulting range of idealized values on the magnitude and phase responses are based on 8 and 7 data sets respectively for driving-point mechanical impedance and apparent mass, while only 4 and 3 data sets respectively were left to define the seat-to-head transmissibility magnitude and phase. (C) 1998 Academic Press.