Ride comfort in vehicles can be affected by seat properties. While previous studies focused on the vertical whole-body vibration, this study was designed to understand the influence of the foam thickness at the seat pan and at the backrest on seat transmissibilities with fore-and-aft vibration. Twelve subjects sitting with or without a vertical backrest were exposed to random fore-and-aft vibration between 1 and 15 Hz with the magnitude of 0.5 ms-2 r.m.s.. It was found that there was no significant difference in the primary resonance frequencies in the fore-and-aft in-line and vertical cross-axis transmissibilities to the seat pan and to the backrest. The resonance frequency in the fore-and-aft in-line transmissibilities to the seat pan and the backrest decreased with increasing thickness of foam at the seat pan and the backrest. Altering the thickness of foam at the seat pan was more effective than changing that at the backrest.
Keywords: Cross-axis response; Polyurethane foam; Seat transmissibility.
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