Experimental investigation of the three dimensional vibration of a small lightweight object

An experimental setup for measuring spatial vibrations of small, lightweight objects is presented. To avoid mass-loading effects caused by conventional transducers, nonintrusive measurements with Laser Doppler Vibrometers (LDVs) are performed. The spatial vibration of a single point is obtained using three coupled single LDVs. The optical axes of the LDVs are orientated such that they are pairwise not parallel and not in one plane and the spatial motion is calculated from the three laser signals. Electrically driven translation stages are used to adjust the position of the measurement point on the object. Using this system, a technical model of a biological joint connecting two ossicles of the human middle ear is investigated. The spatial velocity and displacement of several points on both ossicles is measured and the relative motion between the ossicles, which characterizes the joint, is reconstructed. With the described measurement system, the complex vibration pattern of a small structure can be determined.