Reproducible excitation of string instruments using a robotic arm

Abstract

In string instruments, while the vibrations of the wooden bodies can be mostly described as linear, the excitation mechanism is usually nonlinear. For instance, the frictional forces that excite bowed-string instruments have undergone both theoretical and experimental studies due to the underlying complexity. In order to analyze the vibratory behavior and the radiation pattern of musical instruments, it is often necessary to excite the instruments repetitively under controlled conditions, for which artificial means are customarily used. In this work, the sound production in string instruments is studied with the usage of a computer-controlled robotic arm, which provides high precision in positioning as well as controlled motion with 6 degrees of freedom. Together with a customized 3D-printed clamp-system, it is possible to hold and move objects in order to mimic the gestures of instrumentalists, equipping the arm, for example, with a bow or a plectrum. This systematic experimental approach allows to repeatedly reproduce the player-instrument interaction, either by accurately recreating the player actions or by precisely adjusting one or several control parameters. In this study, the possibility to introduce such a robotic arm for the investigation of string instruments is presented and exemplified using different case studies.