The vertical, fore-and-aft, and lateral seat-to-head transmissibility on an elastic seat: influences of the cross-axis coupling, the vibration magnitude and the backrest.

Vibration transmitted from the cushion to the human head can affect riding comfort and even induce motion sickness during the vertical excitation. Although seat-to-head transmissibility has been investigated using a rigid seat, only biodynamic properties of seated occupant were considered and influence of the seating dynamics was neglected. In this study, the in-line and cross-axis seat-to-head transmissibilities of 14 seated occupants were investigated on an elastic seat with the vertical excitation (1-15 Hz) of three different excitation magnitudes (0.2, 0.4, 0.8 m/s2 r.m.s.). The influence of contacting with or without the backrest on the transmissibilities was also analysed. The primary peak frequencies approximately at 4 Hz of the seat-to-head transmissibilities significantly decreased when increasing the excitation magnitude. When contacting with a backrest, the higher primary peak frequencies were observed in seat-to-head transmissibilities for both the vertical in-line and the fore-and-aft cross-axis directions, compared to the measurements without contacting to the backrest. Seat-to-head transmissibilities measured with an elastic seat in this study differs markedly from those tested on a rigid seat in previous studies. This highlights the necessity of further investigation of the influences of dynamic body-seat interactions on seat-to-head transmissibilities, in order to enhance the insight into riding comfort.