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On the control of virtual violins: Physical modelling and control of bowed string instruments 
KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH. (Music acoustics)
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

  This thesis treats the control of sound synthesis of bowed string instruments based on physical modelling. The work followed two approaches: (a) a systematic exploration of the influence of control parameters (bow force, bow velocity, and bow-bridge distance) on the output of a physical model of the violin, and (b) measurements and analyses of the bowing parameters in real violin playing in order to model and parameterize basic classes of bowing patterns for synthesis control.First a bowed-string model based on modal solutions of the string equation is described and implemented for synthesis of violin sounds. The behaviour of the model is examined through simulations focusing on playability, i.e. the control parameter space in which a periodic Helmholtz motion is obtained, and the variations of the properties of the simulated sound (sound level and spectral centroid) within this parameter space. The response of the model corresponded well with theoretical predictions and empirical expectations based on observations of real performances. The exploration of the model allowed to define optimal parameter regions for the synthesis, and to map sound properties on the control parameters.A second part covers the development of a sensor for measuring the bow force in real violin performance. The force sensor was later combined with an optical motion capture system for measurement of complete sets of bowing parameters in violin performance.In a last part, measurements of the control parameters for basic classes of bowing patterns (sautillé, spiccato, martelé, tremolo) are analyzed in order to propose a realistic control of the sound synthesis. The time evolution of the bowing parameters were modelled by analytical functions, which allowed to describe and control simulated bowing patterns by a limited set of control parameters. For sustained bowing patterns such as détaché, control strategies for basic elements in playing (variations in dynamic level, bow changes) were extracted from exemplary measurements, and simple rules deduced, which allowed extrapolation of parameters to modified bow strokes with other durations and at different dynamic levels.

Abstract [sv]

Denna avhandling behandlar styrning av syntes av stråkinstrument med tillämpningar inom fysikalisk modellering av musikinstrument. Problemet har angripits i två steg, först genom en systematisk undersökning av inflytandet av styrparametrarna i violinspel (stråkkraft, stråkhastighet, och avstånd stråke-stall) på utsignalen från en fysikalisk modell, följt av mätningar och analyser av stråkningsparametrarna i normalt violinspel med syfte att modellera och parameterisera grundläggande klasser av stråkarter för styrning av syntesen.

En modell av interaktionen mellan stråke-sträng har utvecklats baserad på modal syntes och modellen har implementerats för syntes av violintoner. Modellen har utforskats genom simuleringar inriktade dels på spelbarheten, dvs. gränserna för den parameterrymd inom vilken en periodisk Helmholtz-rörelse erhålls, och dels på variationerna hos det syntetiserade ljudets egenskaper (ljudnivå och spektral centroid) inom detta parameterområde.

Modellens egenskaper motsvarade väl de teoretiska prediktionerna och förväntade resultat från observationer av violinster. Utforskningen av modellen gjorde det möjligt att definiera optimala parameterområden för styrning av syntesen, och även avbilda ljudens egenskaper på styrparametrarna.

En sensor för mätning av stråkkraften utvecklades för att kunna genomföra mätningar under normalt spel. Sensorn kombinerades senare med ett optiskt system för rörelseanalys vilket gjorde det möjligt att mäta kompletta uppsättningar av stråkparametrar under spel. Uppmätta styrparametrar för grundläggande klasser av stråkarter (sautillé, spiccato, martelé, tremolo) analyserades för att ge tillgång till realistiska styrförlopp av syntesen. Stråkningsparametrarna modellerades med analytiska funktioner, för att kunna beskriva och styra simulerade stråkningsförlopp med ett begränsat antal modellparametrar. För stråkarter med uthållna toner som détaché utvecklades styrstrategier för grundläggande element i spelet, som ändringar i styrkegrad och stråkväxlingar, utifrån mätningar på typfall. Enkla regler formulerades för att kunna extrapolera parametrarna till modifierade stråk med andra durationer och styrkegrader.

Abstract [fr]

Cette thèse porte sur le contrôle de la synthèse sonore par modélisation physique des instruments à corde frottée. Il se base, d’une part, sur l’exploration systématique de l’influence des paramètres de contrôle (pression d’archet, vitesse de l’archet et distance au chevalet) sur le comportement du modèle, et d’autre part, sur la mesure et l’analyse du contrôle effectif qu’exerce l’instrumentiste afin de modéliser et paramétriser des modes de jeu typiques pour le contrôle de la synthèse.

Un modèle de corde frottée basé sur la résolution modale de l’équation de la corde est d’abord présenté et implémenté pour la synthèse sonore du violon. Le comportement du modèle physique est ensuite examiné en effectuant un grand nombre de simulations et se concentre sur deux aspects : la “jouabilité", c’est-à-dire l’espace des paramètres de contrôle dans lequel un mouvement de Helmholtz périodique est obtenu, et les variations des propriétés du son synthétisé (niveau sonore et centroïde spectral) à l’intérieur de cet espace de paramètres. Un très bon accord a été trouvé entre, d’une part, le résultat des simulations et, d’autre part, les prédictions théoriques ou empiriques basées sur l’expérience des instrumentistes. Cette exploration systématique a permis de définir des régions optimales pour le jeu dans l’espace des paramètres de contrôle et de décrire quantitativement la correspondance entre les propriétés sonores pertinentes et les paramètres de contrôle.

La deuxième partie de ce travail concerne la mise au point d’un capteur pour mesurer la force d’appui de l’archet sur la corde dans un contexte de jeu réel. Le capteur est ensuite combiné avec un système optique de capture du mouvement afin de mesurer les paramètres de jeu du violoniste.

La dernière partie présente l’analyse des mesures de ces paramètres de contrôle pour des modes de jeu typiques (sautillé, spiccato, martelé, tremolo), afin de proposer un contrôle réaliste de la synthèse sonore. L’évolution temporelle des paramètres de jeu est modélisée par des fonctions analytiques, ce qui permet de décrire et de simuler différents modes de jeu par un nombre limité de paramètres. Pour les modes de jeu soutenus tels que le détaché, les mesures permettent de décrire des stratégies de contrôle pour des tâches typiques (variation de niveau sonore, changement de direction d’archet), et des procédures simples ont été déduites, permettant d’extrapoler les paramètres de contrôle afin de changer le niveau sonore ou la durée des coups d’archet.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , xix, 217 p.
Series
Trita-CSC-A, ISSN 1653-5723 ; 2008:17
Keyword [en]
Bowed string, physical modelling, sound synthesis, performance control, violin playing
Keyword [fr]
Corde frottée, modélisation physique, synthèse sonore, contrôle gestuel, violon
Keyword [sv]
Struken sträng, fysikalisk modellering, ljudsyntes, musikutförande, violinspel
National Category
Other Physics Topics Computer Science Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-9424ISBN: 978-91-7415-163-3OAI: oai:DiVA.org:kth-9424DiVA: diva2:113911
Public defence
2008-11-24, Salle Stravinsky, UPMC/ Ircam, 1 Place Igor Stravinsky, Paris, France, 10:30 (English)
Opponent
Supervisors
Note
QC 20100714. Gemensam forskarutbildning KTH och Universite Pierre et Marie Curie (Paris VI).Available from: 2008-11-05 Created: 2008-10-31 Last updated: 2010-07-14Bibliographically approved
List of papers
1. Measuring Bow Force in Bowed String Performance: Theory and Implementation of a Bow Force Sensor
Open this publication in new window or tab >>Measuring Bow Force in Bowed String Performance: Theory and Implementation of a Bow Force Sensor
2009 (English)In: Acta Acoustica united with Acustica, ISSN 1610-1928, Vol. 95, no 4, 718-732 p.Article in journal (Refereed) Published
Abstract [en]

A sensor has been developed which allows measurement of the force exerted by the bow on the string ( bow force) during violin performance. The bow force is deduced from measurement of the transversal force at the termination of the bow hair at the frog. The principle is illustrated with an experiment that demonstrates how the bending of the stick and variations in bow hair tension influence the measurements. The design of the sensor is described and performance characteristics are discussed. A thorough calibration procedure is described and tested. Finally, the use of the sensor is demonstrated through measurements in real playing situations.

Keyword
Bowed string; Calibration procedure; Force sensor; Performance characteristics; Transversal force
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-14120 (URN)10.3813/AAA.918200 (DOI)000268380900014 ()2-s2.0-68849083331 (ScopusID)
Note
QC 20100714Available from: 2010-07-14 Created: 2010-07-14 Last updated: 2010-07-14Bibliographically approved
2. Extraction of bowing parameters from violin performance combining motion capture and sensors
Open this publication in new window or tab >>Extraction of bowing parameters from violin performance combining motion capture and sensors
2009 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, Vol. 126, no 5, 2695-2708 p.Article in journal (Refereed) Published
Abstract [en]

A method is described for measurement of a complete set of bowing parameters in violin performance. Optical motion capture was combined with sensors for accurate measurement of the main bowing parameters (bow position, bow velocity, bow acceleration, bow-bridge distance and bow force) as well as secondary control parameters (bow angles: skewness, inclination and tilt). In addition, other performance features (moments of on/off in bow-string contact, string played, and bowing direction) were extracted. Detailed descriptions of the calculations of the bowing parameters, features and calibrations are given. The described system is capable of measuring all bowing parameters without disturbing the player, allowing for detailed studies of musically relevant aspects of bow control and coordination of bowing parameters in bowed-string instrument performance.

Keyword
bowed string, violin performance, measurement, bowing gestures, motion capture
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-9824 (URN)10.1121/1.3227640 (DOI)000271507000064 ()2-s2.0-70449357433 (ScopusID)
Note
QC 20100714. Uppdaterad från submitted till published (20100714).Available from: 2009-01-09 Created: 2009-01-09 Last updated: 2010-07-14Bibliographically approved

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