Modal analysis and computer aided design studies of acoustic guitar structural designs

Abstract

This study seeks to systematically identify modern Computer Aided Design (CAD) techniques to optimize acoustic guitar design. The study uses traditional design as a starting point for analysis of variations in materials and bracing structures of the front sound plate. CAD techniques are used to model the guitar and provide a broadband input that allows analysis of its modal response. Design optimization occurs in creating the most favorable modal response of the instrument while still maintaining structural integrity through effective support of the forces created by the strings’ tension in the bridge and neck. The measures chosen to help identify the most favorable response are modal density, magnitude of the response at each mode, and the locations of the largest magnitudes. Increased modal density provides a richer timbre while the amplitude of the response determines the relative intensity of the sound projected. Increased modal response in the upper bout of the instrument can improve the timbre of pitches in the upper frequency range of the instrument. After analyzing these measures for multiple variations and iterations of a selected set of structural parameters, an optimal design is suggested. The results show good agreement between experimental modal measurements and computer-aided design modeling.