Papers by Vanna Lisa Coli
The emulation of nonlinearities of audio devices can be achieved by means of a nonlinear convolut... more The emulation of nonlinearities of audio devices can be achieved by means of a nonlinear convolution method, which is based on a particular case of the Volterra series, called the Diagonal Volterra series. The Volterra kernels characterize the
nonlinear audio device being tested, dependent upon the level of the signal that passes through the device. In this paper, a method is presented that approximates Volterra kernels in a "continuous" range of levels by means of an interpolation procedure of an achieved number of measurements. In order to obtain the best emulation for real signals, several parameters were tested. An extension of the
previous Diagonal Volterra model is also developed to an arbitrary order of nonlinearities in order to allow better emulation of harmonics of low and medium frequencies; a particular case for the experiments is presented.
Conference Presentations by Vanna Lisa Coli
The behaviour of the soundboard of electroacoustic tools and musical instruments is being investi... more The behaviour of the soundboard of electroacoustic tools and musical instruments is being investigated from several years. The modelling of such instruments is fundamental in order to determine their acoustic characterization. The determination of nonlinear features of the sound production and propagation allows the definition of acoustical aspects that can't be reproduced with methods based on linear impulse response. A method that allows approximating nonlinear distortions of musical instruments by exploiting the Volterra series model is presented. A Matlab code has been developed in order to test the method on real world audio signals. Results of applications are presented on a series of different wind instruments. Some sound examples are provided.
Typical applications in signal and image processing involve the numerical solution of large–scale... more Typical applications in signal and image processing involve the numerical solution of large–scale linear least squares problems with simple constraints, related to an m × n nonnegative matrix A, m n. When the size of A is such that the matrix is not available in memory and only the operators of the matrix-vector products involving A and A T can be computed, forward– backward methods combined with suitable accelerating techniques are very effective; in particular, the gradient projection methods can be improved by suitable step–length rules or by an extrapolation/inertial step. In this work, we propose a further acceleration technique for both schemes, based on the use of variable metrics tailored for the considered problems. The numerical effectiveness of the proposed approach is evaluated on randomly generated test problems and real data arising from a problem of fibre orientation estimation in diffusion MRI.
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Papers by Vanna Lisa Coli
nonlinear audio device being tested, dependent upon the level of the signal that passes through the device. In this paper, a method is presented that approximates Volterra kernels in a "continuous" range of levels by means of an interpolation procedure of an achieved number of measurements. In order to obtain the best emulation for real signals, several parameters were tested. An extension of the
previous Diagonal Volterra model is also developed to an arbitrary order of nonlinearities in order to allow better emulation of harmonics of low and medium frequencies; a particular case for the experiments is presented.
Conference Presentations by Vanna Lisa Coli
nonlinear audio device being tested, dependent upon the level of the signal that passes through the device. In this paper, a method is presented that approximates Volterra kernels in a "continuous" range of levels by means of an interpolation procedure of an achieved number of measurements. In order to obtain the best emulation for real signals, several parameters were tested. An extension of the
previous Diagonal Volterra model is also developed to an arbitrary order of nonlinearities in order to allow better emulation of harmonics of low and medium frequencies; a particular case for the experiments is presented.