Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: A rough road vibration stimulus was reconstructed on a shaker platform to assess the dynamic comfort of seven seats by six human subjects. The virtual seat method was combined with a paired comparison procedure to assess subjective dynamic seat comfort. The psychometric method of constants, 1-up-1-down Levitt procedure and a 2-up-1-down Levitt procedure were compared experimentally to find the most accurate and efficient paired comparison scheme. A two-track interleaved, 2-up-1-down Levitt procedure was used for the subjective dynamic seat comfort assessment. SEAT value is an objective metric and has been widely used to determine seat vibration isolation efficiency. There was an excellent correlation (R2 = 0.97) between the subjective ratings and estimated SEAT values on the seat top when the values are averaged over the six subjects. This study suggests that the SEAT values, estimated from averaged seat top transmissibility of six carefully selected subjects, could be used to select the best seat for a specific road vibration input. / AFRIKAANSE OPSOMMING: Ses persone het deelgeneem aan ‘n eksperiment, om die dinamiese ritgemak van sewe stoele te karakteriseer. ‘n Rowwe padvibrasie is vir die doel op ‘n skudplatform geherkonstrueer. Subjektiewe ritgemak is bepaal deur die virtuelestoel metode met ‘n gepaarde, vergelykingstoets te kombineer. Die psigometriese metode van konstantes, die 1-op-1-af Levitt procedure en die 2-op- 1-af Levitt procedure is vergelyk om die mees effektiewe en akkurate vergelykingstoets te vind. ‘n Tweebaan, vervlegde , 2-op-1-af Levitt prosedure het die beste resultate gelewer en is gekies vir die subjektiewe evaluasie van dinamiese ritgemak. SEAT-waarde is ‘n objektiewe maatstaf, wat gebruik word om te bepaal hoe effektief ‘n stoel die insittende van voertuigvibrasie isoleer. Daar was ‘n uitstekende korrelasie (R2 = 0.97) tussen subjektiewe dinamiese ritgemakevaluesies en SEAT-waardes in die vertikale rigting op die stoelkussing as die gemiddelde oor die ses persone bereken word. Uit die resultate van hierdie studie blyk dit dat SEAT-waardes, wat bereken is vanaf die gemiddelde sitplektransmissie van die ses persone, wat verteenwoordigend van die teikenbevolking is, gebruik kan word om die beste stoel vir ‘n spesifieke vibrasieinset te kies.

The purpose of the present study was to assess the pressure distribution responses to three hour seating bouts in a standard car seat condition compared to a Comfort Motion Technology (CMT) car seat condition. Twelve males participated in the study. Subjects came in for two separate sessions no more than one week apart. Pressure distribution on the backrest and seat pan was assessed in a three hour seating bout. Pressure variables associated with increased seating comfort were collected across six distinct 28 minute cycles and then averaged across these six cycles. The pressure variables were contact area, peak contact pressure, and force. The CMT car seat condition exhibited greater back contact area (p= .003) and less back peak pressure (p= .003) than the standard car seat condition. In addition, the CMT car seat condition had greater seat peak pressure (p< .001) and greater back force (p< .001) than the standard car seat condition. In conclusion, the CMT car seat condition is more comfortable than the standard car seat condition. / School of Physical Education, Sport, and Exercise Science