Denoting the progressive diminution of a free oscillation due to an expenditure of energy. Damping is used to mean both the cause of the energy loss – friction, eddy currents, etc., – and the progressive decrease in amplitude. The amount of damping is termed critical if the system just fails to oscillate (see diagram). Greater or lesser degrees of damping lead to overdamping and underdamping respectively. The damping factor of underdamped oscillations is the ratio of the amplitude of any one of the damped oscillations to that of the following one. The natural logarithm of the damping factor, the logarithmic decrement, is sometimes quoted.

Damped systems