Resonator Guitar Physics Clue from a Paper Cone

Abstract

Resonator guitars are distinguished by the thin aluminum cone or cones that convert string vibration to air vibration. Substituting paper for that aluminum demonstrates that much of what distinguishes them from other guitars comes from basic features of design rather than particular features of the cone(s). Different cones may be more or less to individual players' liking, and paper is an unlikely choice. However, recorded comparisons to flat-top guitars presented here, including sound files, admittance measurements, spectra, and spectrograms, suggest that the characteristic, identifiable commonality of resonator guitar sound is produced by well-defined frequency components that are not related to the pitch of the strings. A natural hypothesis is that these "other" components come from resonances of parts of the body that are excited by the sudden disturbance created by a pluck. As yet to be determined are which parts contribute most strongly to those sounds and exactly how they are excited.

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