Banjo Drum Physics -- sound experiments and simple acoustics demos

Abstract

11" D mylar heads over a normal range of tensions (DrumDial 85 to 91) and "open-back" backed pots of depths 2", 2 3/4", and 5 5/8" are studied over the range 100 to 2000 Hz. Normal modes and resonant frequencies of the heads and of the pot air separately are easily identified and agree with simple expectations. The present focus is the head - pot air interaction. There is no "gold-plated" example of a pair of head-air interacting modes that are distant in frequency from all others. (Had there been such a pair, their interaction could have been isolated and studied in detail.) Nevertheless, there are a few cases where there are hints of the kind of interactions expected from a simple theory. The investigations also offer several examples of banjo physics, including aspects of bridge position and rim flexibility, and some dramatic examples of the perils of sound recording, including floor bounce and room sound.