The vibration level on the seat or at the base of the seat is
mainly computed using the ISO 2631-12) weighted root mean
square (rms) acceleration (aw), or the vibration dose value (VDV).
The SEAT values can be used to predict the dynamic comfort
of the seat for a certain user population, as some researchers
have found a significant correlation (R2=0.94 and R2=0.97)
between the SEAT values and the subjective comfort rating,
when the results were averaged over 6 subjects5, 6). Dynamic
seat testing can be performed in the field by measuring the
vibration level on the floor and on the seat during normal
vehicle operation, or in a laboratory environment under
controlled conditions. The ISO 10326-1 standard7) gives the
basic requirements to perform seat testing in a laboratory
environment. The tests have to be performed with at least two
subjects, having body weight at the 5th and 95th percentile of
the body weight of the vehicle users’ population, for which
the seat is intended. The seat is mounted on a vibrating
platform and vibration is applied to the seat while the subject
is seated in a standardized posture. The vibration is applied
such that the acceleration power spectral density (PSD) at
the base of the seat is representative of the vehicle for which
the seat is tested. Three trials have to be performed for each
subject, while the suspension is adjusted at mid-travel. Then,
for each subject, the SEAT values are estimated from eq. 1,
using the weighted rms accelerations averaged over the three
trials.