Banjo Rim Sound

Abstract

Four different wood rims are equipped with the same kind of head, tension ring, hooks, nuts, and shoes. Recordings of taps on the rims and heads yield informa-
tion on their stiffness and impact on head vibration. A single neck with its own strings, bridge, tailpiece, and co-rod is attached to one rim after the other. The rims
produce different pluck-sound rise times and sustain, in accord with the physics of weight, stiffness, and coupled oscillators. Timbre variations are complicated. The
combined head-rim systems show slight variations in head resonant frequencies but clear variations in the amplitudes of head motions in response to excitation by the
bridge at different frequencies. The details presumably depend on the proximity in frequency of head and rim modes that can couple strongly because of their matching
geometries. Thus, the rims give each banjo a different sound. Sound samples of taps, plucks, and played tunes are included. Some may conclude that the differences are
not that different from what can be achieved with variations in playing technique and set-up.

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