It happens occasionally that the dynamically balanced impeller of a centri fugal pump produces awkward vibration and sound, which probably result from the elastic vibration of the impeller and housing of the pump. It is necessary to foresee the natural frequencies of them and not to operate the pump with the critical speed. Thlsis a short report on measuring the natural frequencies and damping constant of 700 mm impeller of a centrifugal pump of double suction type, together with the method of integrating the acceleration wave form.