Download Improved adjustable boundary condition for the 2-D finite-difference time-domain mesh The digital waveguide (DWG) mesh is a method for simulating wave propagation in multiple dimensions. Boundary conditions are needed for modeling changes in wave propagation media such as walls and furniture in a room or boundaries of a resonating membrane of a musical instrument. The boundary conditions have been solved for a one-dimensional DWG structure, but there is no known exact solution for the multi-dimensional mesh. In this work, a new boundary structure is introduced for modeling reflection coefficient values −1 ≤ r ≤ 1 in two dimensions. The new method gives remarkably more accurate results than the earlier approximations, especially at the low absolute values of r. At incident angles of Θ < 60o , the absolute error of reflection coefficient r is below 0.1 at frequencies 0.004 < f < 0.222 relative to the sampling frequency and at 60o ≤ Θ ≤ 80o the same result is reached at 0.005 < f < 0.114.
Download Granular analysis/synthesis of percussive drilling sounds This paper deals with the automatic and robust analysis, and the realistic and low-cost synthesis of percussive drilling like sounds. The two contributions are: a non-supervised removal of quasistationary background noise based on the Non-negative Matrix Factorization, and a granular method for analysis/synthesis of this drilling sounds. These two points are appropriate to the acoustical properties of percussive drilling sounds, and can be extended to other sounds with similar characteristics. The context of this work is the training of operators of working machines using simulators. Additionally, an implementation is explained.
Download Digital Audio Device Creation by the use of a Domain Specific Language and a Hardware Abstraction Layer The present paper deals with a framework destined to manage different aspects of the creation of digital audio devices. By means of a domain-specific language modelling aspects like signal processing and user interaction are implemented. The problem of different hardware interfaces is resolved by the definition of a hardware abstraction layer. This layer provides different types of variables and functions. A compiler translates the model referring the functions and variables defined at the hardware abstraction layer. Furthermore, the compiler is able to split the model into different parts that can be run on different hardware components. The communication needed to manage the distributed model is defined and formalized by the framework. A simple example is presented to help explain the framework’s parts, as are the compiler and the execution unit.
Download A Preliminary Model for the Synthesis of Source Spaciousness We present here a basic model for the synthesis of source spaciousness over loudspeaker arrays. This model is based on two experiments carried out to quantify the contribution of early reflections and reverberation to the perception of source spaciousness.
Download Morphing of granular sounds Granular sounds are commonly used in video games but the conventional approach of using recorded samples does not allow sound designers to modify these sounds. In this paper we present a technique to synthesize granular sound whose tone color lies at an arbitrary point between two given granular sound samples. We first extract grains and noise profiles from the recordings, morph between them and finally synthesize sound using the morphed data. During sound synthesis a number of parameters, such as the number of grains per second or the loudness distribution of the grains, can be altered to vary the sound. The proposed method does not only allow to create new sounds in real-time, it also drastically reduces the memory footprint of granular sounds by reducing a long recording to a few hundred grains of a few milliseconds length each.
Download Optimal Integer Order Approximation of Fractional Order Filters Fractional order filters have been studied since a long time,
along with their applications to many areas of physics and engineering. In particular, several solutions have been proposed in
order to approximate their frequency response with that of an ordinary filter. In this paper, we tackle this problem with a new approach: we solve analytically a simplified version of the problem
and we find the optimal placement of poles and zeros, giving a
mathematical proof and an error estimate. This solution shows improved performance compared to the current state of the art and is
suitable for real-time parametric control.
Download A Two Level Montage Approach to Sound Texture Synthesis with Treatment of Unique Events In this paper a novel algorithm for sound texture synthesis is presented. The goal of this algorithm is to produce new examples of a given sampled texture, the synthesized textures being of any desired duration. The algorithm is based on a montage approach to synthesis in that the synthesized texture is made up of pieces of the original sample concatenated together in a new sequence. This montage approach preserves both the high level evolution and low level detail of the original texture. Included in the algorithm is a measure of uniqueness, which can be used for the identification of regions in the original texture containing events that are atypical of the texture, and hence avoid their unnatural repetition at the synthesis stage.
Download Real Time Modeling of Acoustic Propagation in Complex Environments In order to achieve high-quality audio-realistic rendering in complex environments, we need to determine all the acoustic paths that go from sources to receivers, due to specular reflections as well as diffraction phenomena. In this paper we propose a novel method for computing and auralizing the reflected as well as the diffracted field in 2.5D environments. The method is based on a preliminary geometric analysis of the mutual visibility of the environment reflectors. This allows us to compute on the fly all possible acoustic paths, as the information on sources and receivers becomes available. The construction of a beam tree, in fact, is here performed through a look-up of visibility information and the determination of acoustic paths is based on a lookup on the computed beam tree. We also show how to model diffraction using the same beam tree structure used for modeling reflection and transmission. In order to validate the method we conducted an acquisition campaign over a real environment and compared the results obtained with our real-time simulation system.
Download An Extension for Source Separation Techniques Avoiding Beats The problem of separating individual sound sources from a mixture of these, known as Source Separation or Computational Auditory Scene Analysis (CASA), has become popular in the recent decades. A number of methods have emerged from the study of this problem, some of which perform very well for certain types of audio sources, e.g. speech. For separation of instruments in music, there are several shortcomings. In general when instruments play together they are not independent of each other. More specifically the time-frequency distributions of the different sources will overlap. Harmonic instruments in particular have high probability of overlapping partials. If these overlapping partials are not separated properly, the separated signals will have a different sensation of roughness, and the separation quality degrades. In this paper we present a method to separate overlapping partials in stereo signals. This method looks at the shapes of partial envelopes, and uses minimization of the difference between such shapes in order to demix overlapping partials. The method can be applied to enhance existing methods for source separation, e.g. blind source separation techniques, model based techniques, and spatial separation techniques. We also discuss other simpler methods that can work with mono signals.
Download Extended Source-Filter Model for Harmonic Instruments for Expressive Control of Sound Synthesis and Transformation In this paper we present a revised and improved version of a recently proposed extended source-filter model for sound synthesis, transformation and hybridization of harmonic instruments. This extension focuses mainly on the application for impulsively excited instruments like piano or guitar, but also improves synthesis results for continuously driven instruments including their hybrids. This technique comprises an extensive analysis of an instruments sound database, followed by the estimation of a generalized instrument model reflecting timbre variations according to selected control parameters. Such an instrument model allows for natural sounding transformations and expressive control of instrument sounds regarding its control parameters.