The vibration of the piano string which is struck by an elastic hammer, is studied by equivalent electric circuit models of impedance analogy and mobility analogy. When the elasticity of the piano string may be neglected and only the tension is considered, the stiff string can be regarded as an electrical transmission line. The hammer can be expressed as the inductance and the capacitance. In order to get the vibration of the struck string, an analog simulator, based on the model, is designed and used. Waveforms, contact time and maximum struck force are calculated by the simulator. The reason of the appearance of the even harmonics series in the high frequency region, and the method of the adjustment are also shown clearly by means of the simulator. The vertical tension waveforms are determined from the synthesis of shifting the phase of two struck string force waveforms. The velocity waveforms are also determined from the synthesis for the two vertical tension waveforms. The characteristics of these waveforms are shown and compared with measured waveforms. The struck string forces, which reduce the vertical tensions, are calculated from the equivalent circuits. In every case, their waves become very similar to the damped half sinusoidal waves. At last, considerations on energy transmission from the hammer to the string are made. Specially, the efficiency at low frequency region is discussed.
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