Acoustic effects of varying the waist width of violin bridges: A physical experiment

Abstract

We explore the relationship between the bridge waist and sound production in the violin. Models of violin acoustics suggest that the stiffness of this portion of the bridge has a considerable effect on an instrument’s sound production. In practice, the proportions of the waist vary significantly from bridge to bridge and instrument to instrument, which suggests there are many ways that a luthier can influence a bridge’s stiffness. Our experiment connects modeling and real-world instrument sound adjustment. We incrementally remove material symmetrically from the bridge in the waist area, recording sound production at each increment. The bridges are destroyed in the process, which is repeated across multiple bridges. Sound stimuli include a sine wave at the bridge with dampened strings and a weighted bow drawn across freely ringing strings. We map changes in bridge geometry to changes in maximum output and acoustic measures of tone quality across several instruments. Since stiffness correlates with thickness, subject to the nature of the bridge material, there may be optimal shape adjustments for maximizing sound production, tone quality, or both.