Paper Archive

Due to advances in computational power, physical modelling for sound synthesis has gained an increased popularity over the past decades. Although much work has been done to accurately simulate existing physical systems, much less work exists on the use of physical modelling simply for the sake of creating sonically interesting sounds. This work presents a mass-spring network, inspired by existing models of the physical string. Masses have 2 translational degrees of freedom (DoF), and the springs have an additional equilibrium separation term, which together result in highly nonlinear effects. The main aim of this work is to create sonically interesting sounds while retaining some of the natural qualities of the physical string, as opposed to accurately simulating it. Although the implementation exhibits chaotic behaviour for certain choices of parameters, the presented system can create sonically interesting timbres, including nonlinear pitch glides and ‘wobbles’.

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The simulation of a bowed string is challenging due to the strongly non-linear relationship between the bow and the string. This relationship can be described through a model of friction. Several friction models in the literature have been proposed, from simple velocity dependent to more accurate ones. Similarly, a highly accurate technique to simulate a stiff string is the use of finitedifference time-domain (FDTD) methods. As these models are generally computationally heavy, implementation in real-time is challenging. This paper presents a real-time implementation of the combination of a complex friction model, namely the elastoplastic friction model, and a stiff string simulated using FDTD methods. We show that it is possible to keep the CPU usage of a single bowed string below 6 percent. For real-time control of the bowed string, the Sensel Morph is used.

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For physical modelling sound synthesis, many techniques are available; time-stepping methods (e.g., finite-difference time-domain (FDTD) methods) have an advantage of flexibility and generality in terms of the type of systems they can model. These methods do, however, lack the capability of easily handling smooth parameter changes while retaining optimal simulation quality and stability, something other techniques are better suited for. In this paper, we propose an efficient method to smoothly add and remove grid points from a FDTD simulation under sub-audio rate parameter variations. This allows for dynamic parameter changes in physical models of musical instruments. An instrument such as the trombone can now be modelled using FDTD methods, as well as physically impossible instruments where parameters such as e.g. material density or its geometry can be made time-varying. Results show that the method does not produce (visible) artifacts and stability analysis is ongoing.

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Digital musical instruments based on physical modelling have gained increased popularity over the past years. This is partly due to recent advances in computational power, which allow for their real-time implementation. One of the great potentials for digital musical instruments based on physical models, is that one can go beyond what is physically possible and change properties of the instruments which are static in real life. This paper presents a real-time implementation of the dynamic stiff string using finitedifference time-domain (FDTD) methods. The defining parameters of the string can be varied in real time and change the underlying grid that these methods rely on based on the recently developed dynamic grid method. For most settings, parameter changes are nearly instantaneous and do not cause noticeable artefacts due to changes in the grid. A reliable way to prevent artefacts for all settings is under development.

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