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Transfer functions as a basis for the verification of models--variability and restraints
1Department of Occupational Health, Group Biological Effects of Vibration and Noise, Federal Institute for Occupational Safety and Health, Nöldnerstr. 40-42, D-10317, Berlin, Germany.
Clinical Biomechanics (Bristol, Avon)
|March 29, 2001
Summary
Individual biodynamic responses to whole-body vibration vary significantly. Relying on average seat-to-head transfer functions can lead to inaccurate predictions of spinal loads in occupational health and ergonomics.
Area of Science:
- Biomechanics
- Human biodynamics
- Occupational health
Background:
- Biodynamic models are used to describe the human body's response to vibration.
- Existing models are typically validated against average seat-to-head transfer functions.
- The extent to which these average values represent individual responses is not well understood.
Purpose of the Study:
- To investigate the individual variability in human biodynamic responses to whole-body vibration.
- To assess the accuracy of models based on average transfer functions for predicting individual spinal loads.
Main Methods:
- An experimental study involving 39 male subjects exposed to random whole-body vibration.
- Measurements of acceleration at the seat and head in the z-direction.
- Calculation of seat-to-head transfer functions and coherence functions for different postures and vibration intensities.
Main Results:
- Subject posture significantly influenced biodynamic response, particularly the peak transmissibility and its frequency.
- Considerable individual variability was observed in seat-to-head transmissibility.
- While average responses showed no effect of vibration intensity, individual responses varied significantly with intensity.
Conclusions:
- Models validated solely on mean transfer functions may yield misleading predictions of individual spinal loads.
- Accurate prediction of individual spinal loads requires models validated against mean individual transmissibility derived from repeated measurements.
- Averaging individual transfer functions results in a loss of critical information, limiting the applicability in occupational health, ergonomics, and design.