Additional modes in transients of a Balinese Gender dasa plate

Abstract

The initial transient of a Balinese bronze plate of a Gender dasa (metallophone) struck by the instrument’s hammer is examined in detail. The spectrum of the radiated sound as well as that of measurements by an accelerator consist of many more eigenmodes compared to the theoretical values for the bending, longitudinal, axial and torsional wave modes. It shows up that the trapezoid shape of the plate leads to these additional frequencies in the transient spectrum, which disappear in the quasi-steady state. As to each bending mode, there exist at least two additional modes. There seems to be a scattering of the initial impulse at the geometrically unsteady boundaries of the trapezoid, which define new internal borders, where new modes can arise from. The low energy of these modes results in a fast decay, while the fundamental mode is still sustained by the bamboo resonator of the Gender. Computer models show the reasoning for such additional spectra modes in principle using transient impulse simulations. These modes can occur just in the case of a hard struck as the typical playing mode of Bali music, which is known to be more lively than Japanese music and corresponds to the initial transient found here.