Download Physical Constraints for the Control of a Physical Model of a Trumpet In this paper, the control of a physical model of a trumpet is studied. Although this model clearly describes the mechanical and acoustical phenomena that are perceptually relevant, additional constraints must be imposed on the control parameters. In contrast with the model where the tube length can be varied continuously, only seven different tube lengths can be obtained with a real instrument. By studying the physical model and its implementation, different relationships between the control parameters and signal characteristics are identified. These relationships are then used to obtain the best set of tube lengths with respect to a given tuning frequency.
Download Physical Modeling for Spatial Sound Synthesis This contribution combines techniques for sound synthesis and spatial reproduction for a joint synthesis of the sound production and sound propagation properties of virtual string instruments. The generated sound field is reproduced on a massive multichannel loudspeaker system using wave field synthesis techniques. From physical descriptions of string vibrations and sound waves by partial differential equations follows an algorithmic procedure for synthesis-driven wave field reproduction. Its processing steps are derived by mathematical analysis and signal processing principles. Three different building blocks are addressed: The simulation of string vibrations, a model for the radiation pattern of the generated acoustical waves, and the determination of the driving signals for the multichannel loudspeaker array. The proposed method allows the spatial reproduction of synthetic spatial sound without the need for pre-recorded or pre-synthesized source tracks.
Download Matching live sources with physical models This paper investigates the use of a physical model template database as the parameter basis for a MPEG-4 Structured Audio (MP4-SA) codec. During analysis, the codec attempts to match the closest corresponding instrument in the database. In this paper, we emphasize the mechanism enabling this match. We give an overview of the final front end, including the pitch detection stage, and remaining problems are discussed. A draft implementation, written in the Python language is described.
Download Physical Model of the String-Fret Interaction In this paper, a model for the interaction of the strings with the frets in a guitar or other fretted string instruments is introduced. In the two-polarization representation of the string oscillations it is observed that the string interacts with the fret in different ways. While the vertical oscillation is governed by perfect or imperfect clamping of the string on the fret, the horizontal oscillation is subject to friction of the string over the surface of the fret. The proposed model allows, in particular, for the accurate evaluation of the elongation of the string in the two modes, which gives rise to audible dynamic detuning. The realization of this model into a structurally passive system for use in digital waveguide synthesis is detailed. By changing the friction parameters, the model can be employed in fretless instruments too, where the string directly interacts with the neck surface.
Download A Strategy for the Modular Implementation of Physics-Based Models For reasons of practical handling as well as optimization of the processes of development and implementation, it is desirable to realize realtime models of sound emitting physical processes in a modular fashion that reflects an intuitively understandable structure of the underlying scenario. At the same time, in discrete– time algorithms based on physical descriptions, the occurance of non–computable instantaneous feedback loops has to be avoided. The latter obstacle prohibits the naive cross-connection of input– output signal processing blocks. The following paper presents an approach to gain modularity in the implementation of physicsbased models, while preventing non–computable loops, that can be applied to a wide class of systems. The strategy has been realized pratically in the development of realtime sound models in the course of the Sounding Object [1] European research project.
Download Physical Modeling of the Harpsichord Plectrum-String Interaction In this paper, we present a thorough treatment of a harpsichord plectrum-string interaction which allows for large end deflections and both transverse motions of the string. We start from the general equations of motion of a bent beam, and an accurate shape of the plectrum is calculated, agreeing with existing known cantilever beam models when end deflections are assumed small. All the governing forces on the string are considered, and the complete motion of the string up to its release is simulated, allowing for future implementation on physical model sound synthesis of strings. Simulation results agree with what is experienced playing a real harpsichord string.
Download A Physical String Model with Adjustable Boundary Conditions The vibration of strings in musical instruments depends not only on their geometry and material but also on their fixing at the ends of the string. In physical terms it is described by impedance boundary conditions. This contribution presents a functional transformation model for a vibrating string which is coupled to an external boundary circuit. Delay-free loops in the synthesis algorithm are avoided by a state-space formulation. The value of the boundary impedance can be adjusted without altering the core synthesis algorithm.
Download Physically Derived Synthesis Model of a Cavity Tone The cavity tone is the sound generated when air flows over the open surface of a cavity and a number of physical conditions are met. Equations obtained from fluid dynamics and aerodynamics research are utilised to produce authentic cavity tones without the need to solve complex computations. Synthesis is performed with a physical model where the geometry of the cavity is used in the sound synthesis calculations. The model operates in real-time making it ideal for integration within a game or virtual reality environment. Evaluation is carried out by comparing the output of our model to previously published experimental, theoretical and computational results. Results show an accurate implementation of theoretical acoustic intensity and sound propagation equations as well as very good frequency predictions. NOMENCLATURE c = speed of sound (m/s) f = frequency (Hz) ω = angular frequency = 2πf (rads/revolution) u = air flow speed (m/s) Re = Reynolds number (dimensionless) St = Strouhal number (dimensionless) r = distance between listener and sound source (m) φ = elevation angle between listener and sound source ϕ = azimuth angle between listener and sound source ρair = mass density of air (kgm−3 ) µair = dynamic viscosity of air (Pa s) M = Mach number, M = u/c (dimensionless) L = length of cavity (m) d = depth of cavity (m) b = width of cavity (m) κ = wave number, κ = ω/c (dimensionless) r = distance between source and listener (m) δ = shear layer thickness (m) δ ∗ = effective shear layer thickness (m) δ0 = shear layer thickness at edge separation (m) θ0 = shear layer momentum thickness at edge separation (m) C2 = pressure coefficient (dimensionless)
Download The Cpld As A General Physical Modeling Synthesis Engine In this paper we propose a system based on a Complex Programmable Logic Device (CPLD) as a physical modeling synthesis engine and a hardware description language (VHDL) to implement the physical modeling synthesis algorithms. An evaluation of VHDL and CPLD technologies for this application was performed. As an example we have programmed the Karplus-Strong plucked string algorithm using VHDL on an Altera CPLD.
Download Material Design in Physical Modeling Sound Synthesis This paper deals with designing material parameters for physical models. It is shown that the characteristic relation between modal frequencies and damping factors of a sound object is the acoustic invariant of the material from which the body is made. Thus, such characteristic relation can be used for designing damping models for a conservative physical model to represent a particular material.