An inflatable guitar

Abstract

It is readily demonstrated that blocking the soundhole of a steel-string acoustic guitar does not significantly affect the instrument's tone. Wavelength considerations indicate that the high frequencies to which our ears are most sensitive radiate directly from the guitar's soundboard. It is common knowledge among luthiers that, in determining the tone of an instrument, the stiffness and damping properties of the guitar's soundboard are of paramount concern. In this study, the traditional wooden architecture of the guitar's soundboard, typically a spruce veneer reinforced with variable wooden bracing, is replaced on a commercial production instrument with a graphite-epoxy “grill” supporting a thin synthetic polymer membrane under tension. In another instrument, the guitar's traditional wooden soundbox is replaced altogether by a graphite-epoxy soundboard grill backed by an inflatable bladder in the shape of a normal guitar body. Both instruments are demonstrated, and techniques for creating aligned-fiber graphite instrument components with room-temperature “time-set” rather than “thermo-set” epoxy resins are discussed.