SELECTED PUBLICATIONS RELATED TO TIME-DOMAIN MODELLING OF MUSICAL INSTUMENTS
van Walstijn, M. (2010), "Parametric FIR Design of Propagation Loss Filters in Digital Waveguide String Models", IEEE Signal Processing Letters. Vol. 17(9), pp. 795 - 798.
Abstract: One of the attractive features of sound synthesis by physical modeling is the potential to build acoustic-sounding digital instruments that offer more flexibility and different options in its design and control than their real-life counterparts. In order to develop such virtual-acoustic instruments, the models they are based on need to be fully parametric, i.e. all coefficients employed in the model are functions of physical parameters that are controlled either on-line or at the (off-line) design stage. In this letter we show how propagation losses can be parametrically incorporated in digital waveguide string models with the use of zero-phase FIR filters. Starting from the simplest possible design in the form of a three-tap FIR filter, a higher-order FIR strategy is presented and discussed within the perspective of string sound synthesis with digital waveguide models.
BibTeX:
@article{spl10,
  author = {Maarten van Walstijn},
  title = {Parametric FIR Design of Propagation Loss Filters in Digital Waveguide String Models},
  journal = {IEEE Signal Processing Letters},
  year = {2010},
  volume = {17},
  number = {9},
  pages = {795 - 798},
  doi = {http://dx.doi.org/10.1109/LSP.2010.2055855}
}
Orr, S. & van Walstijn, M. (2009), "Modal Representation of the Resonant Body within a Finite Difference Framework for Simulation of String Instruments", In 12th Int. Conference on Digital Audio Effects (DAFx-09), Como, Italy., pp. 213-220.
Abstract: This paper investigates numerical simulation of a string coupled transversely to a resonant body. Starting from a complete finite difference formulation, a second model is derived in which the body is represented in modal form. The main advantage of this hybrid form is that the body model is scalable, i.e. the computational complexity can be adjusted to the available processing power. Numerical results are calculated and discussed for simplified models in the form of string-string coupling and string-plate coupling.
BibTeX:
@inproceedings{dafx09s,
  author = {Sarah Orr and Maarten van Walstijn},
  title = {Modal Representation of the Resonant Body within a Finite Difference Framework for Simulation of String Instruments},
  booktitle = {12th Int. Conference on Digital Audio Effects (DAFx-09), Como, Italy},
  year = {2009},
  pages = {213--220},
  url = {http:\sarc.qub.ac.ukvanwalstijnpubspapers9s.pdf}
}
Chatziioannou, V. & van Walstijn, M. (2008), "A refined physical model of the clarinet using a variable air jet height", In 3rd International Symposium on Communications, Control and Signal Processing (ISCCSP 2008). 12-14 2008., pp. 1297 -1301.
Abstract: A time-domain formulation of a lumped model approximation of a clarinet reed excitation mechanism is presented. The lumped model is based on an analytical representation of the flow within the reed channel, incorporating a contraction coefficient (vena contracta factor) that is defined as the ratio of the effective flow over the Bernoulli flow. This coefficient has been considered to be constant in previous studies focusing on sound synthesis. In this paper it will be treated as a function of the reed opening, varying between 0 and 1 as predicted by boundary layer flow theory. Focussing on a specific mouthpiece geometry, the effect of modelling a variable air jet height on the synthesised sound is analysed.
BibTeX:
@inproceedings{isccsp08b,
  author = {Chatziioannou, V. and van Walstijn, M.},
  title = {A refined physical model of the clarinet using a variable air jet height},
  booktitle = {3rd International Symposium on Communications, Control and Signal Processing (ISCCSP 2008)},
  year = {2008},
  pages = {1297 -1301},
  doi = {http://dx.doi.org/10.1109/ISCCSP.2008.4537426}
}
van Walstijn, M. & Avanzini, F. (2007), "Modelling the Mechanical Response of the Reed-Mouthpiece-Lip System of a Clarinet. Part II: A Lumped Model Approximation", Acta Acustica united with Acustica. Vol. 93, pp. 435-446.
Abstract: A non-linear lumped model of the reed-mouthpiece-lip system of a clarinet is formulated, in which the lumped parameters are derived from numerical experiments with a finite-difference simulation based on a distributed reed model. A discrete-time formulation is presented, and its response is compared to that of the distributed model. In addition, the lumped model is applied in the simulation of clarinet tones, enabling the analysis of the effects of using a pressure-dependent stiffness per unit area on sustained oscillations. The analysed effects and features are in qualitative agreement with player's experiences and experimental results obtained in prior studies.
BibTeX:
@article{aca07,
  author = {Maarten van Walstijn and Federico Avanzini},
  title = {Modelling the Mechanical Response of the Reed-Mouthpiece-Lip System of a Clarinet. Part II: A Lumped Model Approximation},
  journal = {Acta Acustica united with Acustica},
  year = {2007},
  volume = {93},
  pages = {435--446},
  url = {http://www.sarc.qub.ac.uk/~mvanwalstijn/pubs/papers/aca07.pdf}
}
Chatziioannou, V. & van Walstijn, M. (2007), "Reed Vibration Modelling for Woodwind Instrument using a Two-Dimensional Finite Difference Method Approach", In International Symposium on Musical Acoustics (ISMA 2007), Barcelona.
Abstract: The vibration of the reed of a clarinet is investigated. The reed is modelled as a two-dimensional vibrating wooden plate with variable thickness, clamped at one end. The fact that wood is anisotropic, thus having different stiffness moduli along each direction, forces one to make diverse changes to the classical formulation of vibrating plates with a constant stiffness modulus. The interaction of the reed with the mouthpiece lay and the player’s lips is modelled by adding conditional contact forces to the external driving force. The resulting equation of motion is described by a fourth order partial differential equation, which is solved numerically using an implicit, two-dimensional finite difference scheme. The boundary conditions of this scheme have to be consistent with the fact that the reed thickness is not constant, which requires great care in the formulation of the numerical model. The derived distributed model is then used in a series of quasi-static simulations, in order to provide some information regarding the parameters of a lumped model approximation of the reed-mouthpiece-lip system. In particular the effective stiffness per unit area and the effective reed surface are estimated as functions of the driving pressure signal.
BibTeX:
@inproceedings{isma07,
  author = {Vasileios Chatziioannou and Maarten van Walstijn},
  title = {Reed Vibration Modelling for Woodwind Instrument using a Two-Dimensional Finite Difference Method Approach},
  booktitle = {International Symposium on Musical Acoustics (ISMA 2007), Barcelona},
  year = {2007},
  url = {http:\sarc.qub.ac.ukvanwalstijnpubspapers7.pdf}
}
da Silva, A.R., Scavone, G.P. & van Walstijn, M. (2007), "Numerical simulations of fluid-structure interactions in single-reed mouthpieces", The Journal of the Acoustical Society of America. Vol. 122(3), pp. 1798-1809. ASA.
Abstract: Most single-reed woodwind instrument models rely on a quasistationary approximation to describe the relationship between the volume flow and the pressure difference across the reed channel. Semiempirical models based on the quasistationary approximation are very useful in explaining the fundamental characteristics of this family of instruments such as self-sustained oscillations and threshold of blowing pressure. However, they fail at explaining more complex phenomena associated with the fluid-structure interaction during dynamic flow regimes, such as the transient and steady-state behavior of the system as a function of the mouthpiece geometry. Previous studies have discussed the accuracy of the quasistationary approximation but the amount of literature on the subject is sparse, mainly due to the difficulties involved in the measurement of dynamic flows in channels with an oscillating reed. In this paper, a numerical technique based on the lattice Boltzmann method and a finite difference scheme is proposed in order to investigate the characteristics of fully coupled fluid-structure interaction in single-reed mouthpieces with different channel configurations. Results obtained for a stationary simulation with a static reed agree very well with those predicted by the literature based on the quasistationary approximation. However, simulations carried out for a dynamic regime with an oscillating reed show that the phenomenon associated with flow detachment and reattachment diverges considerably from the theoretical assumptions. Furthermore, in the case of long reed channels, the results obtained for the vena contracta factor are in significant disagreement with those predicted by theory. For short channels, the assumption of constant vena contracta was found to be valid for only 40% of the duty cycle.
BibTeX:
@article{jasa07,
  author = {Andrey Ricardo da Silva and Gary P. Scavone and Maarten van Walstijn},
  title = {Numerical simulations of fluid-structure interactions in single-reed mouthpieces},
  journal = {The Journal of the Acoustical Society of America},
  publisher = {ASA},
  year = {2007},
  volume = {122},
  number = {3},
  pages = {1798-1809},
  doi = {http://dx.doi.org/10.1121/1.2759166}
}
van Walstijn, M. (2007), "Wave-based Simulation of Wind Instrument Resonators", IEEE Signal Processing Magazine. Vol. 24(2), pp. 21 -31.
Abstract: This article focuses on modular, wave-based, discrete-time modeling of the resonator oscillations. The main advantage of using a wave-based approach is that it explicitly simulates the way in which waves build up in a real instrument and therefore inherently yields a spatial representation. The wave-based approach also happens to be computationally efficient, mainly due to the fact that lossless traveling of waves in 1-D waveguides can be implemented with very few arithmetic operations
BibTeX:
@article{spm07,
  author = {van Walstijn, M.},
  title = {Wave-based Simulation of Wind Instrument Resonators},
  journal = {IEEE Signal Processing Magazine},
  year = {2007},
  volume = {24},
  number = {2},
  pages = {21 -31},
  doi = {http://dx.doi.org/10.1109/MSP.2007.323261}
}
Bilbao, S. & van Walstijn, M. (2005), "A Finite Difference Plate Model", In International Computer Music Conference (ICMC 2005)., pp. 119-122.
Abstract: In this short paper, a simple flexible difference scheme for the simulation of rectangular plate vibration is presented, alonmg with various implementation details (scheme coefficients, a discussion of boundary condition implementation, explicit stability bounds, and memory and computational demands), and a discussion of features such as moving excitation and readout locations. Sound examples are preesnted.
BibTeX:
@inproceedings{icmc05plate,
  author = {Stefan Bilbao and Maarten van Walstijn},
  title = {A Finite Difference Plate Model},
  booktitle = {International Computer Music Conference (ICMC 2005)},
  year = {2005},
  pages = {119-122}
}
Avanzini, F. & van Walstijn, M. (2004), "Modeling the Mechanical Response of the Reed-Mouthpiece-Lip System of a Clarinet. Part I. A One-Dimensional Distributed Model", Acta Acustica united with Acustica. Vol. 90, pp. 537-547.
Abstract: The motion of a clarinet reed that is clamped to a mouthpiece and supported by a lip is simulated in the time-domain using finite difference methods. The reed is modelled as a bar with non-uniform cross section, and is described using a one-dimensional, fourth-order partial differential equation. The interactions with the mouthpiece lay and the player's lip are taken into account by incorporating conditional contact forces in the bar equation. The model is completed by clamped-free boundary conditions for the reed. An implicit finite difference method is used for discretising the system, and values for the physical parameters are chosen both from laboratory measurements and by accurate tuning of the numerical simulations. The accuracy of the numerical system is assessed through analysis of frequency warping effects and of resonance estimation. Finally, the mechanical properties of the system are studied by analysing its response to external driving forces. In particular, the effects of reed curling are investigated.
BibTeX:
@article{aca04,
  author = {Federico Avanzini and Maarten van Walstijn},
  title = {Modeling the Mechanical Response of the Reed-Mouthpiece-Lip System of a Clarinet. Part I. A One-Dimensional Distributed Model},
  journal = {Acta Acustica united with Acustica},
  year = {2004},
  volume = {90},
  pages = {537--547},
  url = {http://www.sarc.qub.ac.uk/~mvanwalstijn/pubs/papers/aca04.pdf}
}
van Walstijn, M. & Campbell, M. (2003), "Discrete-time modeling of woodwind instrument bores using wave variables", The Journal of the Acoustical Society of America. Vol. 113(1), pp. 575-585. ASA.
Abstract: A method for simulation of acoustical bores, useful in the context of sound synthesis by physical modeling of woodwind instruments, is presented. As with previously developed methods, such as digital waveguide modeling (DWM) [Smith, Comput. Music J. 16, 74?91 (1992)] and the multi convolution algorithm (MCA) [Martínez et al., J. Acoust. Soc. Am. 84, 1620?1627 (1988)], the approach is based on a one-dimensional model of wave propagation in the bore. Both the DWM method and the MCA explicitly compute the transmission and reflection of wave variables that represent actual traveling pressure waves. The method presented in this report, the wave digital modeling (WDM) method, avoids the typical limitations associated with these methods by using a more general definition of the wave variables. An efficient and spatially modular discrete-time model is constructed from the digital representations of elemental bore units such as cylindrical sections, conical sections, and toneholes. Frequency-dependent phenomena, such as boundary losses, are approximated with digital filters. The stability of a simulation of a complete acoustic bore is investigated empirically. Results of the simulation of a full clarinet show that a very good concordance with classic transmission-line theory is obtained.
BibTeX:
@article{jasa03,
  author = {Maarten van Walstijn and Murray Campbell},
  title = {Discrete-time modeling of woodwind instrument bores using wave variables},
  journal = {The Journal of the Acoustical Society of America},
  publisher = {ASA},
  year = {2003},
  volume = {113},
  number = {1},
  pages = {575-585},
  doi = {http://dx.doi.org/10.1121/1.1515776}
}
van Walstijn, M. & Campbell, D. (2002), "Time-Domain Simulation of Reed Woodwinds with Application to Musical Sound Synthesis", In Forum Acusticum Meeting, Sevilla, Spain.
Abstract: Experimental determination of the acoustic impedance of tubular objects using a measurement duct with an array of microphones in its wall is considered. A method is proposed in which the influence of the microphone transfer-functions and the discontinuities in the measurement duct are accounted for via a series of calibration measurements with closed tubes. The effects of varying the number of microphones and calibration tubes is studied. Theoretical results show that uniform spacing of both the microphones and calibration tube lengths yields the smallest error within the effective measurement frequency range.
BibTeX:
@inproceedings{forum02,
  author = {Maarten van Walstijn and D.M. Campbell},
  title = {Time-Domain Simulation of Reed Woodwinds with Application to Musical Sound Synthesis},
  booktitle = {Forum Acusticum Meeting, Sevilla, Spain},
  year = {2002},
  url = {http:\sarc.qub.ac.ukvanwalstijnhomepapers2tds.pdf}
}
van Walstijn, M. & Avanzini, F. (2001), "Determination of the Lumped Parameters of a Non-Linear Clarinet Reed Oscillator using a Finite Difference Approach", In International Symposium on Musical Acoustics (ISMA'01), Perugia, Italy., pp. 221-225.
BibTeX:
@inproceedings{isam01,
  author = {Maarten van Walstijn and Federico Avanzini},
  title = {Determination of the Lumped Parameters of a Non-Linear Clarinet Reed Oscillator using a Finite Difference Approach},
  booktitle = {International Symposium on Musical Acoustics (ISMA'01), Perugia, Italy},
  year = {2001},
  pages = {221-225},
  url = {http:\sarc.qub.ac.ukvanwalstijnpubspapers1.pdf}
}
van Walstijn, M. & Scavone, G. (2000), "The Wave Digital Tonehole Model", In International Computer Music Conference (ICMC 2000), Berlin., pp. 465-468.
BibTeX:
@inproceedings{icmc00,
  author = {Maarten van Walstijn and Gary Scavone},
  title = {The Wave Digital Tonehole Model},
  booktitle = {International Computer Music Conference (ICMC 2000), Berlin},
  year = {2000},
  pages = {465-468},
  url = {http:\sarc.qub.ac.ukvanwalstijnpubspapers0.pdf}
}
van Walstijn, M. & Smith, J. (1998), "Use of truncated in finite impulse response (TIIR) filters in implementing efficient digital waveguide models of flared horns and piecewise conical bores with unstable one-pole filter elements", In International Symposium on Musical Acoustics (ISMA 1998). Leavenworth, Washington., pp. 309-314.
Abstract: We describe computational modeling of flaring horns and piecewise conical bores using ``Truncated Infinite Impulse Response'' (TIIR) digital filtering techniques. The approach yields highly efficient and accurate computational models and is therefore appropriate for real-time simulations of woodwind and brass musical instruments
BibTeX:
@inproceedings{isma98,
  author = {Maarten van Walstijn and Julius Smith},
  title = {Use of truncated in finite impulse response (TIIR) filters in implementing efficient digital waveguide models of flared horns and piecewise conical bores with unstable one-pole filter elements},
  booktitle = {International Symposium on Musical Acoustics (ISMA 1998)},
  year = {1998},
  pages = {309-314},
  url = {http:\sarc.qub.ac.ukvanwalstijnpubspapers8.pdf}
}

Created on 30/03/2011.