
87Human Response to Vehicle Vibration
As the dynamic performance of a seat is a function of frequency, and the fre-
quency of the vibration is a function of the instantaneous driving environment, the
overall seat performance is not constant. For example, a seat will perform better at
isolating vibration at 10 Hz compared to vibration at 5 Hz. If the road roughness
changes in character from producing 10 Hz vibration to 5 Hz vibration, the seat will
change from acting as an isolator to acting as an amplier.
Where most car seats’ dynamic performance is dictated by the characteristics
of the foam from which it is constructed, many commercial-vehicle ...