Analysis of bridge mobility of violins

This paper focuses on the bridge mobility of violins. The mobility, or mechanical admittance, quantifies the efficiency of the instrument body to vibrate when a force is applied to the structure. The computation of the mean mobility, after the Skudrzyk’s mean-value theorem, enables a global characterization of the bridge mobility. The choices made by the luthier, when he builds, restores, or adjusts an instrument, modify the mobility and the mean mobility: this is the signature of the instrument. This study shows that the bridge mobility measurement may be helpful for luthiers to objectively characterize an instrument. Two experimental applications on the violin are presented in the paper: the first one studies the characterization of the same violin in several configurations, corresponding to different positions of the soundpost. The second application studies the effect of a violin mute on both the bridge mobility and the spectral characteristics of the produced sound. This study is a part of the PAFI project, which aims to develop a set of tools dedicated to instrument makers.