The invention provides a
system for determining vibration amplitudes of a
structural element of the car, comprising: an acoustic stimulator, configured to generate an acoustic stimulus having an acoustic period to induce vibrations of the
structural element; at least one OCT device, configured to measure a measurement
signal representative for relative positions of measurement points on the
structural element during the vibrations by projecting a measurement beam on the measurement points and to measure a reference
signal representative for a motion phase of the structural element by projecting a
reference beam on a reference point on the car: and a
processing unit, configured to determine vibration amplitudes of the measurement points on the basis of the reference
signal and the measurement signal, wherein the projections of the measurement beam and the
reference beam are related in time, such that a motion phase represented in the reference.