Is produced on changing from the suction side to the pressure side on hydrostatic displacement machines. Due to the pressure drop or increase that occurs in a very short time. The process is all the harder the steeper the rate of pressure rise during the change (up to 106 bar/s).
The pressure alteration forces produced in this manner cause changing elastic deformation in the force-flow bearing parts; these changes cause mechanical oscillation with an amplitude that increases with the rate of pressure rise, i.e. the structure-borne noise generated as a result becomes louder. On the other hand its frequency depends on the rotation speed and number of displacement units in the machine.