Determination of reference values of apparent mass responses of seated occupants of different body masses under vertical vibration with and without a back support

Patra, S. K.; Rakheja, Subhash; Nélisse, Hugues; Boileau, P.-É.; Boutin, Jérôme

doi:10.1016/j.ergon.2007.10.026

Cited by 19 publications

(24 citation statements)

References 18 publications

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“…[3], [8]), when sitting with a reclined backrest [4], when standing [10], and when supine [11]. It has been reported that the influence of vibration magnitude on the resonance frequency is less when sitting in a car driving posture than when sitting with no backrest support [12]. Inter-subject variability in apparent mass has been reported to be greatest at low magnitudes of vibration, with most variability when supported by a backrest or leaning forward with no backrest, and least variability when sitting upright, either with no backrest or supported by a foam backrest [13].…”

Section: Introductionmentioning

confidence: 99%

Apparent mass of the human body in the vertical direction: Inter-subject variability

Toward

Griffin

2011

Journal of Sound and Vibration

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The biodynamic responses of the seated human body to whole-body vibration vary considerably between people, but the reasons for the variability are not well understood. This study was designed to determine how the physical characteristics of people affect their apparent mass and whether inter-subject variability is influenced by the magnitude of vibration and the support of a seat backrest. The vertical apparent masses of 80 seated adults (41 males and 39 females aged 18 to 65) were measured at frequencies between 0.6 and 20 Hz with four backrest conditions (no backrest, upright rigid backrest, reclined rigid backrest, reclined foam backrest) and with three magnitudes of random vibration (0.5, 1.0 and 1.5 ms -2 r.m.s.). Relationships between subject physical characteristics (age, gender, weight, and anthropometry) and subject apparent mass were investigated with multiple regression models. The strongest predictor of the modulus of the vertical apparent mass at 0.6 Hz, at resonance, and at 12 Hz was bodyweight, with other factors having only a marginal effect. After correction for other variables, the principal resonance frequency was most consistently associated with age and body mass index. As age increased from 18 to 65 years, the resonance frequency increased by up to 1.7Hz, and when the body mass index was increased from 18 to 34 kgm -2 the resonance frequency decreased by up to 1.7 Hz. These changes were greater than the 0.9-Hz increase in resonance frequency between sitting without a backrest and sitting with a reclined rigid backrest, and greater than the 1.0-Hz reduction in resonance frequency when the magnitude of vibration increased from 0.5 to 1.5 ms -2 r.m.s. It is concluded that the effects of age, body mass index, posture, vibration magnitude, and weight should be taken into account when defining the vertical apparent mass of the seated human body.

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Section: Introductionmentioning

confidence: 99%

Apparent mass of the human body in the vertical direction: Inter-subject variability

Toward

Griffin

2011

Journal of Sound and Vibration

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“…6. As a second measure, the participating subjects can be selected or grouped in terms of their body weights in the measurement or during data processing, as was done in some studies 3,8) and in the standardization 2) . This is because the total effective mass (which is strongly associated with body weight) could be correlated with the peak damping factor which can strongly influence averaging discrepancies.…”

Section: Approaches For Minimizing the Response-based Averaging Effectsmentioning

confidence: 99%

“…The dynamic response is most frequently studied by examining the driving-point frequency response functions such as apparent mass and mechanical impedance and the vibration transmissibility functions on the body [2][3][4] . Because these response functions are individual-specific, and they usually vary in a large range [5][6][7][8] , it is frequently desired to derive representative response functions for a group of subjects, such as those participating in a given study. The unweighted arithmetic average is usually used for such a representation.…”

Section: Introductionmentioning

confidence: 99%

“…Alternatively, the representative response function can be derived from a biodynamic property-based approach [8][9][10][11] . With this approach, dynamic properties of each subject are estimated using a mechanical-equivalent model that can be constructed based on the response function, the vibration transmissibility, or both of these biodynamic measures.…”

Section: Introductionmentioning

confidence: 99%

“…The simpler response-based method is certainly the first choice if the results generated by these two approaches are similar. For example, the inter-subject and intra-subject variations of the biodynamic responses measured under the same testing conditions in the same laboratory are usually greater than 10% in the resonance frequency range [5][6][7][8] ; the variations of the inter-laboratory mean data are also usually greater than 10% 3) ; hence, a percent difference of less than 10% between the two approaches at some frequencies is unlikely to be important for many practical applications. Although issues with the response-based method have been raised 9,11) , it is unclear whether the specific averaging discrepancies are beyond an acceptable level.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An Evaluation of the Methods for Deriving Representative Frequency Response Functions of the Human Whole-body System

et al. 2010

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Abstract:The biodynamic response functions of the human whole-body system measured with subjects participating in an experiment are commonly arithmetically averaged and used to represent their mean response functions in many studies. The reported means were further averaged to form the reference means for standardization and various applications. The objectives of this study are to clarify whether this response-based averaging process could significantly misrepresent the characteristics of the original functions, and to explore appropriate methods for deriving representative functions. A set of reported mechanical-equivalent models for 12 subjects was used to derive the vertical and fore-andaft cross-axis response functions expressed in apparent mass. The response-based average was directly compared with the response derived from a property-based derivation method. This study found that the response-based average could differ from the property-based mean response by more than 30%, especially in the fore-and-aft cross-axis response functions. This study also theoretically demonstrated that the discrepancies result from the non-linear relationship between the apparent mass and the properties of a dynamic system. Therefore, the discrepancies depend on the variability of the subjects' dynamic properties. Practically, the discrepancies in the vertical response could be reduced to an acceptable level (e.g., <10%) if a sufficient number of subjects with similar body weights are selected or grouped in the measurement. However, it is very difficult to reduce the discrepancies in the fore-and-aft cross-axis to such a level. While more demanding than the response-based method, the property-based method is theoretically more reliable for deriving the representative response functions for each axis.

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Seat-to-Head Transfer Functions Prediction Using Artificial Neural Networks

Saveljic

2023

Applied Artificial Intelligence: Medicine, Biology, Chemistry, Financial, Games, Engineering

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Determination of reference values of apparent mass responses of seated occupants of different body masses under vertical vibration with and without a back support

Cited by 19 publications

References 18 publications

Apparent mass of the human body in the vertical direction: Inter-subject variability

Apparent mass of the human body in the vertical direction: Inter-subject variability

An Evaluation of the Methods for Deriving Representative Frequency Response Functions of the Human Whole-body System

Seat-to-Head Transfer Functions Prediction Using Artificial Neural Networks

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