The violin sound output effect involves many aspects such as the acoustic structure of the instrument, string vibration, and so on. In this paper, based on the theoretical knowledge of vibration and Helmholtz motion, the mass-spring model of bow-string interaction is established. The physical phenomena are revealed by a non-contact optical measurement system, and the spectrogram of the bow-string interaction is obtained to analyze the sound output effect of the violin. The results show that the captured images are processed and analyzed to show that the vibration of both the G-string pulling and the E-string pulling motions are characterized by attenuation. The pulling direction is not strictly along the Y direction, and some components are in the X-Y and X-Z planes. The displacement waveforms show that the average vibration periods of the pulled G and pulled E strings are about 5 ms and 1.5 ms, respectively. The strings with average onset of vibration duration were E > A > D > G strings, and the overall amplitude of E and A strings > D and G strings, respectively.
