On today’s vehicles it becomes ever more challenging to measure (vibro-)acoustic frequency response functions (FRF) for noise path contribution or experimental modal analysis. Vehicles have more and more damping material, leading to reduced noise and vibration levels, also during modal testing or (reciprocal) FRF measurement. The widely adopted (burst) random excitation techniques are often unable to excite the structure at sufficiently high levels resulting in signal-to-noise ratio problems, long measurement times (many averages) and noisy FRFs. High quality FRFs can be measured using stepped sine excitation techniques, that are able to concentrate the excitation energy at a single frequency and excite the structure at much higher energy levels. However, the current implementation of these techniques is rather slow with measurement times that are a multiple of (burst) random techniques and as such are not often used.
Therefore, a new MIMO (multiple input multiple output) sine testing technique has been developed that allows to have the high excitation levels (and resulting high quality FRF data) of a stepped sine technique, but at drastically reduced measurement times. This new technique is compared with stepped sine and burst random techniques with relation to data quality and measurement time using industrial application cases.
