In a string musical instrument (guitar or violin) in playing conditions, the forces applied by the strings on the body are at the origin of the radiated sound. The aim of the study is to define a methodology to record these forces in real time while the musician is playing. More precisely, the method focuses on estimating the equivalent forces at each string/bridge coupling point. Such equivalent forces are those which, applied at the bridge, would create the same velocity field on the soundboard. The methodology will be presented for the simulation of a single string coupled to a beam. The numerical simulation of the method allows its robustness to be assessed. Three applications can be identified: comparison of instruments, listening to non-playable instruments and study of the instrumental playing by analyzing the measured equivalent force.
