Resonances of a Violin Body Studied by Hologram Interferometry and Acoustical Methods

Abstract

Hologram interferometry is applied to study resonances of a violin body. A violin is made and after each major step, modes of vibration are studied. The top plate is studied in six steps: without and with f-holes, with f-holes and bass bar, with an artificial sound post, in the assembled instrument without and with strings. The back plate is studied in four steps: without and with artificial sound post, in the assembled instrument without and with strings. Interferograms of the lowest five to seven modes ranging from about 400 to 1 300 Hz are shown. The top plate is shown to be divided into plate and body resonances. The back plate is acting more as a unit together with the ribs thus mainly giving body-resonances. Deformations of the violin are studied when strings are pressed against the fingerboard, by double exposure hologram interferometry. The lowest air resonance of the sounding box and frequency responses are acoustically measured. In playing the unvarnished violin the tone is found powerful and even.