Mechanical Impedance Properties of a Toy Xylophone and Two Steel Drums

Abstract

A series of informal measurements of the mechanical driving point impedance properties of a toy xylophone and two steel drums is described. The motivating factor for these measurements was to establish the feasibility of accurate identification of the fundamental pitches for the various segmented regions of the steel drum from mechanical impedance data. Complicating factors, which limit the accuracy of these measurements, are indicated. It is shown that interesting mechanical properties of the toy xylophone can readily be demonstrated. Successful measurements were conducted upon a large steel drum which indicate that: (I) the fundamental component of the free decay or the frequency for the lowest principal resonance is nominally a major third above the indicated pitch, but that (II) variations from this tuning of ± 1 semitone are common in the lowest octave; (III) variations of ± 3 semitone are common in the upper octave; and (IV) the subjective impression of tonal purity is correlated with the absence of modal degeneracy or coupling in the fundamental mechanical resonance.