Mechanical noises are created by the dynamic forces of the rotating and oscillating components and by the movement of components within their running clearance, e.g. piston – cylinder and bearing journal – bearing shell. In the crankgear, gas and inertia forces overlap and lead to the excitation of indirect combustion noises.

The measurement of these movements together with their resulting structure-borne sound excitation is carried out using noncontact travel sensors on an eddy-current basis.