Download Transforming Vibrato Extend in Monophonic Sounds
This paper describes research into signal transformation operators allowing to modify the vibrato extent in recorded sound signals. A number of operators are proposed that deal with the problem taking into account different levels of complexity. The experimental validation shows that the operators are effective in removing existing vibrato in real world recordings at least for the idealized case of long notes and with properly segmented vibrato sections. It shows as well that for instruments with significant noise level (flute) independent treatment of noise and harmonic signal components is required.
Download Harpsichord Sound Synthesis using a Physical Plectrum Model Interfaced with the Digital Waveguide
In this paper, we present a revised model of the plectrum-string interaction and its interface with the digital waveguide for simulation of the harpsichord sound. We will first revisit the plectrum body model that we have proposed previously in [1] and then extend the model to incorporate the geometry of the plectrum tip. This permits us to model the dynamics of the string slipping off the plectrum more comprehensively, which provides more physically accurate excitation signals. Simulation results are presented and discussed.
Download Modelling of Brass Instrument Valves
Finite difference time domain (FDTD) approaches to physical modeling sound synthesis, though more computationally intensive than other techniques (such as, e.g., digital waveguides), offer a great deal of flexibility in approaching some of the more interesting real-world features of musical instruments. One such case, that of brass instruments, including a set of time-varying valve components, will be approached here using such methods. After a full description of the model, including the resonator, and incorporating viscothermal loss, bell radiation, a simple lip model, and time varying valves, FDTD methods are introduced. Simulations of various characteristic features of valve instruments, including half-valve impedances, note transitions, and characteristic multiphonic timbres are presented, as are illustrative sound examples.
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 High-Rate Data Hiding Technique for Audio Signals based on INTMDCT Quantization
Data hiding consists in hiding/embedding binary information within a signal in an imperceptible way. In this study we propose a high-rate data hiding technique suitable for uncompressed audio signals (PCM as used in Audio-CD and .wav format). This technique is appropriate for non-securitary applications, such as enriched-content applications, that require a large bitrate but no particular robustness to attacks. The proposed system is based on a quantization technique, the Quantization Index Modulation (QIM) applied on the Integer Modified Discrete Cosine Transform (IntMDCT) coefficients of the signal and guided by a PsychoAcoustic Model (PAM). This technique enables embedding bitrates up to 300 kbps (per channel), outperforming a previous version based on regular MDCT.
Download Mapping blowing pressure and sound features in recorder playing
This paper presents a data-driven approach to the construction of mapping models relating sound features and blowing pressure in recorder playing. Blowing pressure and sound feature data are synchronously obtained from real performance: blowing pressure is measured by means of a piezoelectric transducer inserted into the mouth piece of a modified recorder, while produced sound is acquired using a close-field microphone. Acquired sound is analyzed frame-by-frame, and features are extracted so that original sound can be reconstructed with enough fidelity. A multi-modal database of aligned blowing pressure and sound feature signals is constructed from real performance recordings designed to cover basic performance contexts. Out of the gathered data, two types of mapping models are constructed using artificial neural networks: (i) a model able to generate sound feature signals from blowing pressure signals, and therefore used to produce synthetic sound from recorded blowing pressure profiles via additive synthesis; and (ii) a model able to estimate the blowing pressure from extracted sound features.
Download Nonlinear Allpass Ladder Filters in FAUST
Passive nonlinear filters provide a rich source of evolving spectra for sound synthesis. This paper describes a nonlinear allpass filter of arbitrary order based on the normalized ladder filter. It is expressed in FAUST recursively in only two statements. Toward the synthesis of cymbals and gongs, it was used to make nonlinear waveguide meshes and feedback-delay-network reverberators.
Download A Csound Opcode for a Triode Stage of a Vacuum Tube Amplifier
The Csound audio programming language adheres to the inputoutput paradigm and provides a large number of specialized commands (called opcodes) for processing output signals from input signals. Therefore it is not directly suitable for component modeling of analog circuitry. This contribution describes an attempt to virtual analog modeling and presents a Csound opcode for a triode stage of a vacuum tube amplifier. Externally it communicates with other opcodes via input and output signals at the sample rate. Internally it uses an established wave digital filter model of a standard triode. The opcode is available as library module.
Download Generalized Reassignment with an Adaptive Polynomial-Phase Fourier Kernel for the Estimation of Non-Stationary Sinusoidal Parameters
This paper describes an improvement of the generalized reassignment method for estimating the parameters of a modulated real sinusoid. The main disadvantage of this method is decreased accuracy for high log-amplitude and/or frequency changes. One of the reasons for such accuracy deterioration stems from the use of the Fourier transform. Fourier transform belongs to a more general family of integral transforms and can be defined as an integral transform using a Fourier kernel function - a stationary complex sinusoid. A correlation between the Fourier kernel function and a non-stationary sinusoid decreases as the modulation of the sinusoid increases, ultimately causing the parameter estimation deterioration. In this paper, the generalized reassignment is reformulated for use with an arbitrary kernel. Specifically, an adaptive polynomial-phase Fourier kernel is proposed. It is shown that such an algorithm needs the parameter estimates from the original generalized reassignment method and that it improves the Signalto-Residual ratio (SRR) in the non-noisy cases. The drawbacks concerning the initial conditions and ways of avoiding a close-tosingular system of linear equations are discussed.
Download Signal Reconstruction from STFT magnitude : a State of the Art
This paper presents a review on techniques for signal reconstruction without phase, i.e. when only the spectrogram (the squared magnitude of the Short Time Fourier Transform) of the signal is known. The now standard Griffin and Lim algorithm will be presented, and compared to more recent blind techniques. Two important issues are raised and discussed: first, the definition of relevant criteria to evaluate the performances of different algorithms, and second the question of the unicity of the solution. Some ways of reducing the complexity of the problem are presented with the injection of additional information in the reconstruction. Finally, issues that prevents optimal reconstruction are examined, leading to a discussion on what seem the most promising approaches for future research.