12,145 research outputs found
A digital waveguide-based approach for Clavinet modeling and synthesis
The Clavinet is an electromechanical musical instrument produced in the mid-twentieth century. As is the case for other vintage instruments, it is subject to aging and requires great effort to be maintained or restored. This paper reports analyses conducted on a Hohner Clavinet D6 and proposes a computational model to faithfully reproduce the Clavinet sound in real time, from tone generation to the emulation of the electronic components. The string excitation signal model is physically inspired and represents a cheap solution in terms of both computational resources and especially memory requirements (compared, e.g., to sample playback systems). Pickups and amplifier models have been implemented which enhance the natural character of the sound with respect to previous work. A model has been implemented on a real-time software platform, Pure Data, capable of a 10-voice polyphony with low latency on an embedded device. Finally, subjective listening tests conducted using the current model are compared to previous tests showing slightly improved results
Algorithms and VLSI architectures for parametric additive synthesis
A parametric additive synthesis approach to sound synthesis is advantageous as it can model sounds in a large scale manner, unlike the classical sinusoidal additive based synthesis paradigms. It is known that a large body of naturally occurring sounds are resonant in character and thus fit the concept well. This thesis is concerned with the computational optimisation of a super class of form ant synthesis which extends the sinusoidal parameters with a spread parameter known as band width. Here a modified formant algorithm is introduced which can be traced back to work done at IRCAM, Paris. When impulse driven, a filter based approach to modelling a formant limits the computational work-load. It is assumed that the filter's coefficients are fixed at initialisation, thus avoiding interpolation which can cause the filter to become chaotic. A filter which is more complex than a second order section is required. Temporal resolution of an impulse generator is achieved by using a two stage polyphase decimator which drives many filterbanks. Each filterbank describes one formant and is composed of sub-elements which allow variation of the formant’s parameters. A resource manager is discussed to overcome the possibility of all sub- banks operating in unison. All filterbanks for one voice are connected in series to the impulse generator and their outputs are summed and scaled accordingly. An explorative study of number systems for DSP algorithms and their architectures is investigated. I invented a new theoretical mechanism for multi-level logic based DSP. Its aims are to reduce the number of transistors and to increase their functionality. A review of synthesis algorithms and VLSI architectures are discussed in a case study between a filter based bit-serial and a CORDIC based sinusoidal generator. They are both of similar size, but the latter is always guaranteed to be stable
Multi-scale FEM-DEM model for granular materials : micro-scale boundary conditions, statics and dynamics
A FEM-DEM model for granular material
Cosmology from Topological Defects
The potential role of cosmic topological defects has raised interest in the
astrophysical community for many years now. In this set of notes, we give an
introduction to the subject of cosmic topological defects and some of their
possible observable signatures. We begin with a review of the basics of general
defect formation and evolution, we briefly comment on some general features of
conducting cosmic strings and vorton formation, as well as on the possible role
of defects as dark energy, to end up with cosmic structure formation from
defects and some specific imprints in the cosmic microwave background radiation
from simulated cosmic strings. A detailed, pedagogical explanation of the
mechanism underlying the tiny level of polarization discovered in the cosmic
microwave background by the DASI collaboration (and recently confirmed by WMAP)
is also given, and a first rough comparison with some predictions from defects
is provided.Comment: Lecture Notes delivered at the Xth Brazilian School on Cosmology and
Gravitation, Mangaratiba, Rio de Janeiro, July 29 - August 9, 2002. To appear
in the proceedings (AIP Press), edited by M. Novello and S. Perez Bergliaffa.
Updated source files with high resolution figures available at
http://www.iafe.uba.ar/relatividad/gangui/xescola
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