Collisions in double string plucked instruments: Physical modelling and sound synthesis of the viola caipira

• Published in: Journal of sound and vibration Vol. 443; pp. 178 - 197
• Main Authors: Paiva, Guilherme Orelli, Ablitzer, Frédéric, Gautier, François, Campos dos Santos, José Maria
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 17-03-2019; Elsevier Science Ltd; Elsevier
• Subjects: Acoustics; Collisions; Computer simulation; Engineering Sciences; Finite difference method; Guitars; High speed cameras; Hybrid model; Music; Simulation; Sound; Sound synthesis; String musical instruments; Strings; Synthesis; Vibration analysis; Viola caipira; Viola caipira; Hybrid model; String musical instruments; Collisions; Sound synthesis
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1016/j.jsv.2018.11.012

The viola caipira is a folk guitar widely used in traditional and modern Brazilian music. It consists, in general, of 10 metallic strings arranged in five pairs, tuned in unison or octave, with the thinnest string located in the middle. An experimental study of the viola caipira pluck by means of a high speed camera reveals some specificities of the instrument. It is found that the instrument is characterized by a double pluck excitation since the two strings of a given pair are plucked successively and rapidly. Collisions between strings arranged in the same pair are identified. A hybrid model, based on a modal approach, is carried out for sound synthesis purposes. It includes 10 strings with non-planar motions coupled with the body and collisions between strings. A finite difference scheme is used to compute the coupling forces at each time-step, which permits a set of sound simulations. The effects of string/string collisions on the viola caipira sounds are identified and discussed. It is found that the model reproduces the main vibroacoustic features of the viola caipira, among which the sympathetic string resonances and the string/string collisions observed in the video analysis.