| The violin has long been the subject of experimentation in attempts to quantitatively describe it. Doing so could inform the luthier in constructing a better instrument. To that end a planar near-field acoustic holography (NAH) system is designed and implemented to produce images of acoustic sources at the source surface. The system's viability is tested using a simple 2 dimensional disk sound source excited by a force sensing impact hammer. In reconstructions at the source surface, pressure fields are found to exhibit good acoustic source localization. The system is then applied to violin surface imaging. The arching of the violin top, approximately 15 mm, will inevitably yield errors in reconstructions using the planar near-field holography system. The relation of the signal to noise ratio to the distance of the measurement plane from the source surface is shown to be paramount to the success of the NAH application in determining the spatial resolution of reconstructed images.;A student Chinese violin, selected for its evenness across the strings in playing tests, is employed in the NAH process. The A0, A1, B1+, and B1- modes, known to play major roles in sound radiation, are identified and tracked through three violin states: violin (1) supported freely with a sound post, (2) supported freely without a post and (3) supported with post in a clamped fixture designed to resemble forces applied by the violinist during playing. The A0 mode is shown to drop by 40 Hz and increase in power with the removal of the sound post. The clamped support fixture case shows a decrease in energy density in the 400 -- 500 and 700 -- 2000 Hz range. The potential for the NAH process to couple acoustic radiation source visualizations on the violin surface to the known radiating modes is examined. |
