On the structural and acoustic design of guitar soundboards
Davis, Evan Brugh, 1955-
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An assumed mode model of a guitar soundboard has been built and experimentally verified. The frequency range of interest was from 55 to 880 Hertz, covering the frequency range of the fundamentals of the notes played on the guitar. The guitar soundboard is modeled as an orthotropic plate reinforced with tapered beams using the Rayleigh-Ritz technique. Sound power spectra are computed using the radiation impedance of an equivalent array of piston sources and the velocity distribution computed from the forced vibration analysis of the soundboard coupled to a backing cavity and soundhole. The prediction model is compared to an experimental guitar which was documented by recording mode shapes, Chladni patterns, at 25 steps in the assembly process. The material properties used in the prediction programs were determined experimentally. The major findings of the study were: (1) the bracing system dominates the vibration pattern of the soundboard, (2) bracing patterns are required to improve the radiation efficiencies of the unbraced plates, (3) material property variations in the bracing materials can significantly influence the soundboard's dynamics and (4) plate materials and plate finishes have no significant impact on the radiated sound power spectrum in the modeled range.
- Mechanical engineering