The first peak in the frequency response function (a ratio between the sound pressure at 1 m from a guitar and mechanical impulse at the bridge) is assumed to be a Fast Fourier Transformation (denoted as p’) of sound pressure changes due to damped oscillation of a virtual and hybrid mechanical-acoustic system (m-b-k-A). This consists of a mass (discrete mass m), damper (coefficient of viscous damping b) and spring (stiffness k) which are variables, and a massless membrane with area A (surface A) which is a constant. Depending on its position, a 20 gram weight placed on the top board variously affected amplitude, frequency, and damping of p’. Thus, the position of the weight influences the system dynamics, which is defined through the mechanical quantities m, b and k. A high degree of inverse proportionality between the first guitar mode intensity (or amplitude of p’) on the one hand and coefficient of viscous damping b on the other hand was measured. A consequence of this feature works well in modeling and optimizing of the first guitar mode [1, 2]: At coordinates on a guitar top for which the weight results in relatively high b the brace results in relatively low b and consequently in relatively high intensity and low damping of the analyzed mode.Full Text
Article published Jun 13, 2011.
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The Savart Journal is published in collaboration with the Guild of American Luthiers.