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It has been widely reported that the overall vibration comfort performance of static and dynamics seats is strongly influenced by the biodynamic behaviour of the seated human body. The contributions of the seated occupant to the overall vibration attenuation of the coupled seat-occupant system are experimentally investigated as functions of the nature of excitation, static and dynamic properties of the seat, and the sitting posture. The study involved two different seats with natural frequencies in the vicinity of 1.5 Hz and 4 Hz, which would characterize the low natural frequency suspension as well as high natural frequency seats employed in automobiles and some industrial vehicles. The vibration isolation properties of the seats are evaluated with a rigid mass and two human subjects under different vibration excitations, including swept sine, broad-band random and standardized vibration spectra of selected vehicles.

The comfort assessments of automotive seats are attempted through development of seat-occupant models in order to minimize the participation of human subjects in such studies. A nonlinear model of a polyurethane foam (PUF) cushion and its support mechanism is developed through measurement of static and dynamic properties as functions of the seated load, and excitation frequencies and amplitudes. Nonlinear analytical models of the seat-occupant system are developed by integrating three different occupant models of different complexities with the cushion model. The analytical response characteristics of these models are derived under sinusoidal and random excitations considered representative of the automotive vibration environment. The vibration transmission properties of the seat are measured in the laboratory under harmonic and random excitations using 6 human subjects.