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A physics-based modeling approach for vibrato on fretted and non-fretted string instruments
Orientador(es)
Resumo(s)
Vibrato is part of the subtle musical expressions frequently used by musicians to convey emotions during musical performance. Physically, it is a low-frequency modulation superimposed to the pitch of a musical tone, which has a strong perceptual role as it also affects the overall frequency spectrum. Obviously, the playing technique differs according to the instruments. For bowed string instruments, it is performed by changing periodically the string singing length through a rocking motion of a finger on a string. However, for fretted instruments such as guitars, vibrato is different because the frets impose the acoustic length of the string. Classical guitarists therefore push and pull the string periodically to modify the string tension, thereby altering the pitch. In this paper, we extent our modal-based sound synthesis techniques developed for string instruments to provide a physical model of fretted and non-fretted instruments with vibrato playing. Vibrato is introduced on a physical basis, by including cyclic variations of either the string tension or the position of artifical fingers constraining the string locally, and no numerical artefact is included. The modeling work exploits the benefits of the modal approach, which especially appears adequate to handle the variations in string tension as an external pseudo-excitation. We briefly present our time-domain numerical model for the plucked string problem, and then address the implementation issues. The cases of a both vibrato techniques are considered, and extension of the model to include nonlinear geometrical effects is presented based on the KirchoffCarrier equations, since it considers the nonlinearity coming as change of the string tension. Finally, an attempt is made to compute the sound radiation by convolution, combining the computed force exerted by the string at the bridge with a measured vibro-acoustic impulse response. Results stemming from numerical time-domain simulations are presented to illustrate the rationale and efficiency of the approach.
Descrição
UID/EAT/00472/2013
Palavras-chave
Contexto Educativo
Citação
Editora
SEA - Sociedad Española de Acústica