Download A Method of Generic Programming for High Performance DSP
This paper presents some key concepts for a new just in time programming language designed for high performance DSP. The language is primarily intended to implement an updated version of PWGLSynth, the synthesis extension to the visual musical programming environment PWGL. However, the system is suitable for use as a backend for any DSP platform. A flow control mechanism based on generic programming, polymorphism and functional programming practices is presented, which we believe is much better suited for visual programming than traditional loop constructs found in textual languages.
Download The Jamoma Audio Graph Layer
Jamoma Audio Graph is a framework for creating graph structures in which unit generators are connected together to process dynamic multi-channel audio in real-time. These graph structures are particularly well-suited to spatial audio contexts demanding large numbers of audio channels, such as Higher Order Ambisonics, Wave Field Synthesis and microphone arrays for beamforming. This framework forms part of the Jamoma layered architecture for interactive systems, with current implementations of Jamoma Audio Graph targeting the Max/MSP, PureData, Ruby, and AudioUnit environments.
Download Real-Time 3D Finite-Difference Time-Domain Simulation of Low- and Mid-Frequency Room Acoustics
Modern graphics processing units (GPUs) are massively parallel computing environments. They make it possible to run certain tasks orders of magnitude faster than what is possible with a central processing unit (CPU). One such case is simulation of room acoustics with wave-based modeling techniques. In this paper we show that it is possible to run room acoustic simulations with a finite-difference time-domain model in real-time for a modest-size geometry up to 7kHz sampling rate. For a 10% maximum dispersion error limit this means that our system can be used for realtime auralization up to 1.5kHz. In addition, the system is able to handle several simultaneous sound sources and a moving listener with no additional cost. The results of this study include performance comparison of different schemes showing that the interpolated wideband scheme is able to handle in real-time 1.4 times the bandwidth of the standard rectilinear scheme with the same maximum dispersion error.
Download MultiBin: A Binaural Audition Tool
MultiBin is a new tool for binaural audition of multiple sound sources in a user definable environment. Although designed to be flexible in its application, its primary function is to provide dynamic multi-channel binaural simulation. It is built upon two new Csound binaural reverberation opcodes. An early reflection opcode, based on an image source method and a Head-Related Transfer Function interpolation algorithm previously introduced by the authors provides dynamic source and listener location. This is complemented by a later reverberation opcode which provides a diffuse reverb based on a parametric Feedback Delay Network model which considers interaural coherence.
Download Digital Simulation of “Brassiness” and Amplitude-Dependent Propagation Speed in Wind Instruments
The speed of sound in air increases with pressure, causing pressure peaks to travel faster than troughs, and leading to a sharpening of the propagating pressure waveform. Here, this nonlinear effect is explored, and its application to brass instrument synthesis and its use as an audio effect are described. Acoustic measurements on tubes and brass instruments are presented showing significant spectral enrichment, sometimes referred to as “brassiness.” The effect may be implemented as an amplitudedependent delay, distributed across a cascade of incremental delays. A bidirectional waveguide, having a pressure-dependent delay, appropriate for musical instrument synthesis, is presented. A computationally efficient lumped-element processor is also presented. Example brass instrument recordings, originally played softly, are spectrally enriched or “brassified” to simulate a fortissimo playing level.
Download Acoustic Modelling of a Convex Pipe Adapted for Digital Waveguide Simulation
This work deals with the physical modelling of acoustic pipes for real-time simulation, using the “Digital Waveguide Network” approach and the horn equation. With this approach, a piece of pipe is represented by a two-port system with a loop which involves two delays for wave propagation, and some subsystems without internal delay. A well-known form of this system is the “Kelly-Lochbaum” framework, which allows the reduction of the computation complexity. We focus this work on the simulation of pipes with a convex profile. But, using the “Kelly-Lochbaum” framework with the horn equation, two problems occur: first, even if the outputs are bound, some substates have their values which diverge; second, there is an infinite number of such substates. The system is then unstable and cannot be simulated as such. The solution of this problem is obtained with two steps. First, we show that there is a simple standard form compatible with the “Waveguide” approach, for which there is an infinite number of solutions which preserve the input/output relations. Second, we look for one solution which guarantees the stability of the system and which makes easier the approximation in order to get a low-cost simulation.
Download Energy Based Synthesis of Tension Modulation in Membranes
Above a certain amplitude, membrane vibration becomes nonlinear due to the variation of surface tension. This leads to audible pitch glides, which greatly contribute to the characteristic timbre of tom-tom drums of the classical drum set and many other percussion instruments. Therefore, there is a strong motivation to take the tension modulation effect into account in drum synthesis. Some models do already exist that model this phenomenon, however, their computational complexity is significantly higher compared to linear membrane models. This paper applies an efficient methodology previously developed for the string to model the quasistatic part (short-time average) of the surface tension. The efficient modeling is based on the linear relationship between the quasistatic tension and membrane energy, since the energy can be computed at a relatively low computational cost. When this energy-based tension modulation is added to linear membrane models, the perceptually most relevant pitch glides are accurately synthesized, while the increase in computational complexity is negligible.
Download Spatial Sound Synthesis for Circular Membranes
Physical models of real or virtual instruments are usually only exploited for the generation of wave forms. However, models of twoand three-dimensional vibrating structures contain also information about the sound radiation into the free field. This contribution presents a model for a membrane from which the required driving functions for a multichannel loudspeaker array are derived. The resulting sound field reproduces not only the musical timbre of the sounding body but also its spatial radiation characteristics. It is suitable for real-time synthesis without pre-recorded or presynthesized source tracks.
Download More Modal Fun - “Forced Vibration” at One Point
The question, if a vibrating object can be forced to follow a given movement profile at one point forms a case of an inverse problem. It is shown that for the specific setting of an object described by modal data, this question may be solved by a newly developed method. The new technique has several strengths, such as allowing to compute modal data for the constrained scenario and forming a basis for precise and stable simulations. The latter potential is shown at a short example, a stiff string being hammered against a fixed board by a hammer of infinite mass.
Download Modeling Methods for the Highly Dispersive Slinky Spring: A Novel Musical Toy
The ’Slinky’ spring is a popular and beloved toy for many children. Like its smaller relatives, used in spring reverberation units, it can produce interesting sonic behaviors. We explore the behavior of the ’Slinky’ spring via measurement, and discover that its sonic characteristics are notably different to those of smaller springs. We discuss methods of modeling the behavior of a Slinky via the use of finite-difference techniques and digital waveguides. We then apply these models in different structures to build a number of interesting tools for computer-based music production.