Some mechanical and acoustical consequences of the violin soundpost

Mechanical and acoustical consequences of removal of the soundpost in the violin were examined using (a) experimental modal analysis on a violin with (SP) and without soundpost (no-SP) to examine the approximately 50 modes observed over a 0- to 2-kHz range and (b) boundary element radiation calculations of radiation efficiency and directivity for each normal mode. A majority of modes were tracked between SP and no-SP states by correlating frequency, damping, mode shape, and interviolin MAC values. On removal of the soundpost, (a) mode frequencies below 1 kHz usually dropped a few percent, while those above increased similarly, (b) average mechanical response at the bridge increased 14%, (c) average radiation efficiency dropped 17%, most noticeably from 500 to 800 Hz, especially for a very strong corpus SP mechanical mode at ∼550 Hz whose radiation efficiency dropped from 0.105 to 0.022, and (d) radiation patterns altered substantially. A vibration-radiation model to simulate response curves agreed well with general features of previous SP violin response and radiativity measurements, and with Fourier analysis of recorded SP and no-SP slide tones. Calculated SP radiation patterns were also compared to previous violin directivity measurements.