Modification of the guitar bracing using optimization

The form of modern guitars were shaped by Spanish luthiers in the XIX century. Especially Antonio de Torres Jurado is the one, whose designs are an inspiration for modern constructions. From the very beginning, guitars are struggling with not sufficient sound levels for all the desired applications. Apart from electroacoustic amplification, there were several attempts to modify the construction of the sound hole or the soundboard. Higher sound pressure levels were often connected with distorted sound, sometimes not acceptable to musicians. In this paper, inequalities in the frequency characteristics of the sound generated by the guitar with modern sound holes are presented. Resonant frequencies of the soundboard were pointed as being responsible for the too high amplitude of sound in the 600-800 Hz frequency range. Using optimization and finite element method modelling, the best patterns of bracings were proposed to equalize the frequency spectrum and improve the sound of the instrument.