Physical modelling of a harp from Central Africa

Abstract

Central Africa harps are string instruments, often anthropomorphic, serving an essential cultural role. Compared to pedal harps, their body is small in size with a soundboard mainly made of animal skin and a neck made of a wood beam. In this paper, a physical model is developed as a tool for assessing the specificities of these musical instruments, from a vibro-acoustic perspective. The modeling strategy is based on the modal Udwadia-Kalaba formalism which is a multibody substructuring technique. Input modal parameters of the body and the strings are experimentally identified and the main steps of the estimation procedures are detailed. The reliability of the physical model is investigated via the comparison between simulated and experimental data for several plucking configurations. Different hypotheses are assessed such as the string/neck coupling which proves to strongly influence the dynamic response of the body when there is a coincidence between string and neck modal frequencies. The inclusion of geometrical nonlinearities proves to be of major importance, even for a weak plucking, as it allows qualitative representation of double frequency terms in the simulations. Overall, physical simulations of the soundboard motion are in good agreement with measurements indicating characteristic features of the instrument are captured.