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The concept of impedance of mechanical elements is presented by the analogy to electric circuits. The impedance concept makes the whole field of circuit analysis with its highly developed circuit rules, theorems, and mathematics available for the solution of mechanical problems. Because the calculation of the impedance of most structures is very difficult, a direct measurement of impedance can simplify the problem. Several devices for this measurement are presented. Then, a computer and recorder is shown which calculates and plots impedance information as the measurement is being made. Finally, examples are presented where velocities at points on a simple structure are predicted for sinusoidal excitation and the shock-excited velocity response of a mass mounted on sponge rubber is predicted from impedance information.

Too much attention has been given to the analysis of the transient disturbances to which present day electronic gear is exposed. It does not necessarily follow that such extremely detailed examinations lead to practical engineering procedures which will produce equipment resistant to or be immune to such transient excitations. Much more attention should be given to reduce this wealth of material to a level where designers of equipment can formulate yardsticks which can be a part of the many other accepted standard procedures and which are now common practice in order to build equipment compatible with certain environments.