Synthesis of performance expression of bowed string instruments using “Expression Mark Functions”
Yuma Koizumi, Katunobu Itou · The Journal of the Acoustical Society of America · 2012
This paper proposes a method for synthesis of performance expression of bowed string instruments. In order to reflect a creator's intention on a synthetic sound, physical model is efficient because the sound can be synthesized by the performance imagination. The physics of the bowed string instruments are still some issues remain unresolved, bowed string sound synthesis using only the physical model is difficult. In this paper, a method using a transfer function for expression mark is proposed. “Expression mark functions” is estimated from recorded performance sounds, using spectrum of string motion and inverse filter of resonant properties of the instruments. Bowed String motion is a triangular wave called the Helmholtz wave, and it can be determined from bowed string position. Changes of waveform from expression performance were estimated by non-negative matrix factorization. Resonant properties of an instrument were measured as TSP response using a “direct conduction speaker”. The expression mark functions of the performance is extracted by decomposing the actual performance. For evaluation of the quality of the synthesized sound, the scale by ten kinds of expression marks was synthesized using expression mark functions, and the questionnaire estimated the degree of agreement in five steps.