Download Transaural 3-D audio with user-controlled calibration
A calibration method allowing users to customize the loudspeaker layout for 2-, 4-, and 5.1-channel playback, and to steer the “sweet spot” to the position o f the listener’s head is presented. The method, which is applied to a computationally efficient transaural 3D audio system for dynamic spatialization o f multiple sound sources, is based on u ser interaction and auditory feedback. The robustness of the a uditory sensation is analyzed for small displacements of the listener near the sweet spot. A modification of the system permits continuous adjustment of the sweet spot size by the listener. The modification limits the a rtifacts due to the transaural processing for positions away from the sweet spot. For wide settings, the system gradually reduces to a discrete amplitude panning system.
Download A reverberator based on absorbent all-pass filters
Artificial reverberator topologies making use of all-pass filters in a feedback loop are popular, but have lacked accurate control of decay time and energy level. This paper reviews a general theory of artificial reverberators based on Unitary-Feedback Delay Networks (UFDN), which allow accurate control of the decay time at multiple frequencies in such topologies. We describe the design of an efficient reverberator making use of chains of elementary filters, called “absorbent all-pass filters”, in a feedback loop. We show how, in this particular topology, the late reverberant energy level can be controlled independently of the other control parameters. This reverberator uses the I3DL2 control parameters, which have been designed as a standard interface for controlling reverberators in interactive 3D audio.
Download A parallel 3D digital wave guide mesh model with tetrahedral topology for room acoustic simulation
Following a summary of the basic principles of 3D waveguide mesh modelling and the context of its application to room acoustic simulation, this paper presents a detailed analysis of the tetrahedral mesh topology and describes its implementation on a parallel computer model. Its structural characteristics are analysed, with particular emphasis on how they influence execution speed. Performance deterioration due to communication overhead in the parallelised model is discussed. Theoretical predictions are compared with data from performance tests carried out on different computer platforms and both are contrasted with the corresponding results from the rectilinear model, in order to assess the practical efficiency of the model. Objective validation tests are reported and discussed.
Download Multi-loudspeaker reverberation system
In this paper we present a reverberation system based on a multiloudspeaker configuration. The aim of this work is to produce a natural sounding reverberation system with a similar pattern to the produced in real rooms. A new method for sound spatialization is presented, and it is used to locate on the virtual room’s surfaces the early reflections produced in a reverberant space. Each loudspeaker is fed with its corresponding early reflection sequence after the panning process, and an artificial late reverberation is added in each channel, obtaining a more realistic experience that the obtained with other artificial reverberation systems.
Download Enhanced 3D sound field synthesis and reproduction system by compensating interfering reflections
The antique stereophonic recording and playback format is going to be replaced by new surround sound formats in the near future. At the moment, various surround techniques are being investigated in many artistic and technical applications. The main concern is to find an appropriate recording and playback format which supports the natural spatial hearing cues. Therefore, surround sound systems should provide a homogeneous and coherent sound field image, both for recorded and synthesized sound fields [1]. In a homogeneous sound reproduction system, no direction is treated preferentially. Coherent sound field image means that the image remains stable under changes of the listener position, though the image may change as a natural sound field does. The Holophony and Ambisonic system described by Nicol and Emerit [2] is the basic approach. This system will be extended by a new approach to compensate the interfering reflections of the reproduction room. Further possibilities to determine higher order Ambisonic signals using the beam forming approach are investigated.
Download Statistical approach for sounds modeling
This article introduces a mathematical approach to extracting some statistical parameters from noise-like sounds. This approach could define a new spectral model or extend existing ones to analyze and synthesize such complex sounds. In the future, this method could also permit electro-acoustic composers to make musical transformations. We have performed several synthesis tests with synthetic and natural sounds using these parameters. The main assumptions is that analyzed sounds must not contain any transient or slow-varying deterministic component. The natural sounds resynthesized during our experiments sounds like the original ones even if some defects are perceptible because of the analysis limitations. We propose some initial solutions for future works.
Download A system for data-driven concatenative sound synthesis
In speech synthesis, concatenative data-driven synthesis methods prevail. They use a database of recorded speech and a unit selection algorithm that selects the segments that match best the utterance to be synthesized. Transferring these ideas to musical sound synthesis allows a new method of high quality sound synthesis. Usual synthesis methods are based on a model of the sound signal. It is very difficult to build a model that would preserve the entire fine details of sound. Concatenative synthesis achieves this by using actual recordings. This data-driven approach (as opposed to a rule-based approach) takes advantage of the information contained in the many sound recordings. For example, very naturally sounding transitions can be synthesized, since unit selection is aware of the context of the database units. The C ATERPILLAR software system has been developed to allow data-driven concatenative unit selection sound synthesis. It allows high-quality instrument synthesis with high level control, explorative free synthesis from arbitrary sound databases, or resynthesis of a recording with sounds from the database. It is based on the new software-engineering concept of component-oriented software, increasing flexibility and facilitating reuse.
Download Harmonic-band wavelet coefficient modeling for pseudo-periodic sounds processing
In previous papers [1], [2] we introduced a model for pseudo-periodic sounds based on Wornell results [3] concerning the synthesis of 1/f noise by means of the Wavelet transform (WT). This method provided a good model for representing not only the harmonic part of reallife sounds but also the stochastic components. The latter are of fundamental importance from a perceptual point of view since they contain all the information related to the natural dynamic of musical timbres. In this paper we introduce a refinement of the method, making the spectralmodel technique more flexible and the resynthesis coefficient model more accurate. In this way we obtain a powerful tool for sound processing and cross-synthesis.
Download Flexible software framework for modal synthesis
Modal synthesis is an important area of physical modeling whose exploration in the past has been held back by a large number of control parameters, the scarcity of generalpurpose design tools and the difficulty of obtaining the computational power required for real-time synthesis. This paper presents an overview of a flexible software framework facilitating the design and control of instruments based on modal synthesis. The framework is designed as a hierarchy of polymorphic synthesis objects, representing modal structures of various complexity. As a method of generalizing all interactions among the elements of a modal system, an abstract notion of energy is introduced, and a set of energy transfer functions is provided. Such abstraction leads to a design where the dynamics of interactions can be largely separated from the specifics of particular modal structures, yielding an easily configurable and expandable system. A real-time version of the framework has been implemented as a set of C++ classes along with an integrating shell and a GUI, and is currently being used to design and play modal instruments, as well as to survey fundamental properties of various modal algorithms.
Download 3D graphics tools for sound collections
Most of the current tools for working with sound work on single soundfiles, use 2D graphics and offer limited interaction to the user. In this paper we describe a set of tools for working with collections of sounds that are based on interactive 3D graphics. These tools form two families: sound analysis visualization displays and model-based controllers for sound synthesis algorithms. We describe the general techniques we have used to develop these tools and give specific case studies from each family. Several collections of sounds were used for development and evaluation. These are: a set of musical instrument tones, a set of sound effects, a set of FM radio audio clips belonging to several music genres, and a set of mp3 rock song snippets.