Soundpost Thesis

THE EFFECT OF THE SOUNDPOST ON VIOLIN SOUND

The sound output and the response of a violin were measured for three positions of the soundpost: no soundpost, inside and outside the treble foot of the bridge. The sound quality was assessed with Long Time Average Spectra that showed small differences. There were significant differences in the response plots, whether measured by a microphone in front of the top or a magnet/coil pickup on the bridge.

These results may be related to previous studies, in which the stiffness of the top plate at the bridge foot positions was measured for different soundpost positions. At the bass foot position, the stiffness did not change appreciably for these different soundpost positions. At the treble foot position, the stiffness was lower when the soundpost was placed inside the treble foot, and higher when it was placed outside.

INTRODUCTION

The bridge is mounted between the f-holes of the violin. If there were no mechanical support, the region of the top plate between the f-holes would be rather more compliant than the rest of the body. Two mechanical supports are present, however.

An extended series of measurements on this violin is shown in figure 2 for this violin. It can be seen that the stiffnesses at positions measured from the soundhole suggest, for this violin, that the stiffness at the treble foot position is above that at the bass foot position when the soundpost is outside the treble foot. When the soundpost is inside the treble foot, the stiffness at the treble foot position is below that at the bass foot position. This is illustrated in figure 2. The stiffness at the bass foot remains constant. Other violins have not shown this effect as clearly. Distance from treble soundhole (nearer surfaces). T/F = position of treble foot, in