Savart Journal

science and technology of stringed musical instruments

Modeling and Optimizing of the First Guitar Mode

Samo Sali

Abstract

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.

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Article published Jun 13, 2011.
This article has been accessed 8558 times since publication.

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The Savart Journal is published in collaboration with the Guild of American Luthiers.

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Samo Sali
http://saliguitars.com/
Slovenia


Samo Sali was born in Kranj, Slovenia in 1965. He finished secondary school Gimnazija Kranj in 1984 and started to study at Faculty of Mechanical Engineering, Ljubljana in 1985. In 1993 he defended his diploma thesis about influence of cutting processes on the acoustic properties of wooden resonant boards. In the same year and at same institution he continued his career as a researcher at the Department of Manufacturing Technologies. Better understanding of guitar acoustics was supported with 9 classes of guitar at Music school Vic-Rudnik between 1988-1996. In 1997 he successfully finished his Master thesis where he defined a criterion for guitar sound definition called "rule of consonance-dissonance" which was also published in scientific literature. 2 years later Samo Sali finished his Doctor thesis where he presented algorithm for guitar sound optimization. Between 1999 and 2001 he was a head assistant at the Department of Technology Management. In 2002 he left his position at Faculty of Mechanical Engineering and started with guitar making in cooperation with Croatian guitar maker Mr. Mirko Hotko. In 2005 the Ministry of Culture of Republic of Slovenia granted him a status of independent guitar maker. Since then Samo Sali develops and builds Sali guitars in his own workshop in Ljubljana, Slovenia.