Download Real-Time Implementation of an Elasto-Plastic Friction Model using Finite-Difference Schemes 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.
Download Flexible Real-Time Reverberation Synthesis With Accurate Parameter Control Reverberation is one of the most important effects used in audio
production. Although nowadays numerous real-time implementations of artificial reverberation algorithms are available, many of
them depend on a database of recorded or pre-synthesized room
impulse responses, which are convolved with the input signal. Implementations that use an algorithmic approach are more flexible
but do not let the users have full control over the produced sound,
allowing only a few selected parameters to be altered. The realtime implementation of an artificial reverberation synthesizer presented in this study introduces an audio plugin based on a feedback delay network (FDN), which lets the user have full and detailed insight into the produced reverb. It allows for control of
reverberation time in ten octave bands, simultaneously allowing
adjusting the feedback matrix type and delay-line lengths. The
proposed plugin explores various FDN setups, showing that the
lowest useful order for high-quality sound is 16, and that in the
case of a Householder matrix the implementation strongly affects
the resulting reverberation. Experimenting with delay lengths and
distribution demonstrates that choosing too wide or too narrow a
length range is disadvantageous to the synthesized sound quality.
The study also discusses CPU usage for different FDN orders and
plugin states.
Download Dynamic Grids for Finite-Difference Schemes in Musical Instrument Simulations 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.
Download A Physical Model of the Trombone Using Dynamic Grids for Finite-Difference Schemes In this paper, a complete simulation of a trombone using finitedifference time-domain (FDTD) methods is proposed. In particular, we propose the use of a novel method to dynamically vary the
number of grid points associated to the FDTD method, to simulate
the fact that the physical dimension of the trombone’s resonator
dynamically varies over time. We describe the different elements
of the model and present the results of a real-time simulation.
Download Real-Time Implementation of a Friction Drum Inspired Instrument Using Finite Difference Schemes Physical modelling sound synthesis is a powerful method for constructing virtual instruments aiming to mimic the sound of realworld counterparts, while allowing for the possibility of engaging
with these instruments in ways which may be impossible in person.
Such a case is explored in this paper: particularly the simulation
of a friction drum inspired instrument. It is an instrument played
by causing the membrane of a drum head to vibrate via friction.
This involves rubbing the membrane via a stick or a cord attached
to its center, with the induced vibrations being transferred to the
air inside a sound box.
This paper describes the development of a real-time audio application which models such an instrument as a bowed membrane
connected to an acoustic tube. This is done by means of a numerical simulation using finite-difference time-domain (FDTD) methods in which the excitation, whose position is free to change in
real-time, is modelled by a highly non-linear elasto-plastic friction
model. Additionally, the virtual instrument allows for dynamically
modifying physical parameters of the model, thereby allowing the
user to generate new and interesting sounds that go beyond a realworld friction drum.
Download Real-Time Implementation of the Dynamic Stiff String Using Finite-Difference Time-Domain Methods and the Dynamic Grid 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.
Download Nonlinear Strings based on Masses and Springs 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’.