Inharmonic Partials and Banjo Ring

Abstract

Banjo sound is rich in inharmonic partials, i.e., strong frequency components of a plucked note that are not integer multiples of the pitch frequency. Their origins are identified here by experiments that reveal how their amplitudes can be reduced. And the results are as simple as possible: inharmonic partials overwhelmingly come from the vibration modes of the head and the other strings. The sudden bridge disturbance at the onset of a pluck produces the sound of a gentle head tap and a soft version of the sound of the other unplucked strings. Rim vibrations are also identified but do not play a significant roll in this aspect of the sound. It is suggested that inharmonic partials are the long-conjectured source of the ring of the banjo. With the origin of those partials established, the connection to “ring” becomes a question of psychacoustics.

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