Download Model-based synthesis and transformation of voiced sounds In this work a glottal model loosely based on the Ishizaka and Flanagan model is proposed, where the number of parameters is drastically reduced. First, the glottal excitation waveform is estimated, together with the vocal tract filter parameters, using inverse filtering techniques. Then the estimated waveform is used in order to identify the nonlinear glottal model, represented by a closedloop configuration of two blocks: a second order resonant filter, tuned with respect to the signal pitch, and a regressor-based functional, whose coefficients are estimated via nonlinear identification techniques. The results show that an accurate identification of real data can be achieved with less than regressors of the nonlinear functional, and that an intuitive control of fundamental features, such as pitch and intensity, is allowed by acting on the physically informed parameters of the model. 10
Download A Numerical Scheme for Various Nonlinear Forces, Including Collisions, Which Does Not Require an Iterative Root Finder Nonlinear forces are ubiquitous in physical systems, and of prominent importance in musical acoustics. Though many models exist to describe such forces, in most cases the associated numerical schemes rely on iterative root finding methods, such as NewtonRaphson or gradient descent, which are computationally expensive and which therefore could represent a computational bottleneck. In this paper, a model for a large class of nonlinear forces is presented, and a novel family of energy-conserving finite difference schemes given. The schemes only require the evaluation of the roots of a quadratic function. A few applications in the lumped case are shown, and the robustness and accuracy of the scheme tested.
Download An expressive real-time sound model of rolling This paper describes the structure and potential of a real-time sound model of “rolling”. The work has it’s background and motivation in the ecological approach of psychoacoustics. Scope of interest is the efficient and clear (possibly exaggerated) acoustic expression, cartoonification, of certain ecological attributes rather than realistic simulations for their own sake. To this end, different techniques of sound generation are combined in a hybrid hierarchical structure. A physics-based algorithm (section 2) of impact-interaction at the audio-core is surrounded by higher-level structures that explicitely model macroscopic characteristics (section 5). Another connecting audio-level algorithm, the “rolling-filter”, reduces the (3-dimensional) geometry of the rolling-contact to the one dimension of the impactinteraction-model (section 3).
Download Real-Time Reverb Simulation Using Arbitrary Models We present a method for simulating reverberation in real-time using arbitrary object shapes. This method is an extension of digital plate reverberation where a dry signal is filtered through a physical model of an object vibrating in response to audio input. Using the modal synthesis method, we can simulate the vibration of many different shapes and materials in real time. Sound samples are available at the follwing website: http://cynthia.code404.com/dafx-audio/.
Download Digital Synthesis Models of Clarinet-Like Instruments Including Nonlinear Losses in the Resonator This paper presents a real-time algorithm for the synthesis of reed instruments, taking into account nonlinear losses at the first open tonehole. The physical model on which the synthesis model relies on is based on the experimental works of Dalmont et al. who have shown that for high pressure levels within the bore, an air jet obeying the Bernoulli flow model, hence acting as a nonlinear resistance, is created at the open end of the bore. We study the effect of these additional losses on the response of the bore to an acoustic flow impulse at different levels and on the self oscillations. We show that at low frequencies, these nonlinear losses are of the same order of magnitude than the viscothermal linear losses and modifie the functioning of the whole instrument. For real-time synthesis purposes, a simplified algorithm is proposed and compared to the more accurate model.
Download A Finite Difference Model for Articulated Slide-String Simulation Slide-string instruments allow continuous control of pitch by articulation with a slide object whose position of contact with the
string is time-varying. This paper presents a method for simulation of such articulation. Taking into account sensing and musical
practice considerations, an appropriate physical model configuration is determined, which is then formulated in numerical form
using a finite difference approach. The model simulates the attachment and detachment phases of slide articulation which generally involve rattling, while finger damping is modelled in a more
phenomenological manner as a regionally induced time-varying
damping. A stability bound for the numerical model is provided
via energy analysis, which also reveals the driving power contributions of the separate articulatory sources. The approach is exemplified with simulations of slide articulatory gestures that involve
glissando, vibrato and finger damping.
Download Decomposition of steady state instrument data into excitation system and formant filter components This paper describes a method for decomposing steady-state instrument data into excitation and formant filter components. The input data, taken from several series of recordings of acoustical instruments is analyzed in the frequency domain, and for each series a model is built, which most accurately represents the data as a source-filter system. The source part is taken to be a harmonic excitation system with frequency-invariant magnitudes, and the filter part is considered to be responsible for all spectral inhomogenieties. This method has been applied to the SHARC database of steady state instrument data to create source-filter models for a large number of acoustical instruments. Subsequent use of such models can have a wide variety of applications, including wavetable and physical modeling synthesis, high quality pitch shifting, and creation of “hybrid” instrument timbres.
Download Sparse Decomposition, Clustering and Noise for Fire Texture Sound Re-Synthesis In this paper we introduce a framework that represents environmental texture sounds as a linear superposition of independent foreground and background layers that roughly correspond to entities in the physical production of the sound. Sound samples are decomposed into a sparse representation with the matching pursuit algorithm and a dictionary of Daubechies wavelet atoms. An agglomerative clustering procedure groups atoms into short transient molecules. A foreground layer is generated by sampling these sound molecules from a distribution, whose parameters are estimated from the input sample. The residual signal is modelled by an LPC-based source-filter model, synthesizing the background sound layer. The capability of the system is demonstrated with a set of fire sounds.
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 Experimental Study of Guitar Pickup Nonlinearity In this paper, we focus on studying nonlinear behavior of the pickup of an electric guitar and on its modeling. The approach is purely experimental, based on physical assumptions and attempts to find a nonlinear model that, with few parameters, would be able to predict the nonlinear behavior of the pickup. In our experimental setup a piece of string is attached to a shaker and vibrates perpendicularly to the pickup in frequency range between 60 Hz and 400 Hz. The oscillations are controlled by a linearizion feedback to create a purely sinusoidal steady state movement of the string. In the first step, harmonic distortions of three different magnetic pickups (a single-coil, a humbucker, and a rail-pickup) are compared to check if they provide different distortions. In the second step, a static nonlinearity of Paiva’s model is estimated from experimental signals. In the last step, the pickup nonlinearities are compared and an empirical model that fits well all three pickups is proposed.