Modal studies in a double second Caribbean steel drum
Uwe J. Hansen, Thomas D. Rossing · The Journal of the Acoustical Society of America · 1989
Caribbean steel drums characteristically contain several sections of separately tuned areas imbedded in one quasihemispherically shaped drum head that is formed in the end of a 55-gallon steel drum. The double second pan under study for this report includes three A♭ sections tuned in octaves. Pitch and spectral content for each section depend on section geometry, mass distribution, and elastic properties. Section geometry is determined by hammer-embossed boundary delineation while mass and tension are modified by selective hammering in the section interior, which enables tuning of several lower partials harmonically. Spectral nearfield studies illustrate harmonic content as well as departures from harmonicity in some of the notes under study. Time average holographic interferometry shows strong amplitude dependence of spectral content of notes and illustrates coupling between sections. Complications in using impact excited modal analysis due to noncoherent input contributions are discussed, and computer-animated modes are illustrated.