A simple and rapid method of Elasticity Measurement is described. The test piece is set on the metalic base, inserting the thin insulating material between them. The longitudinal vibration of the piece is catched by the crystal pick-up and is transformed into the electrical energy. The induced voltage in the pick-up is amplified and is applied between the piece and the base. Thus the piece continues to vibrate with its own natural frequency. The natural frequency of the piece is measured by the specially devised frequency meter.
Among the density p, the Young's Modulus E, the length l and the natural frequency f, there exists the following relation, E =4l²f²p. E, therefore, can be calculated by measuring the natural frenquency f, so long as l and p are known. Indeed, this method can be called the energy feed back method and is speeially fitted for the factory testing.