Download Resynthesis of coupled piano strings vibrations based on physical modeling This paper presents a technique to resynthesize the sound generated by the vibrations of two piano strings tuned to a very close pitch and coupled at the bridge level. Such a mechanical system produces doublets of components generating beats and double decays on the amplitudes of the partials of the sound. We design a waveguide model by coupling two elementary waveguide models. This model is able to reproduce perceptually relevant sounds. The parameters of the model are estimated from the analysis of real signals collected directly on the strings by laser velocimetry. Sound transformations can be achieved by modifying relevant parameters and simulate physical situations.
Download A Parametric Model of Piano Tuning A parametric model of aural tuning of acoustic pianos is presented in this paper. From a few parameters, a whole tessitura model is obtained, that can be applied to any kind of pianos. Because the tuning of piano is strongly linked to the inharmonicity of its strings, a 2-parameter model for the inharmonicity coefficient along the keyboard is introduced. Constrained by piano string design considerations, its estimation requires only a few notes in the bass range. Then, from tuning rules, we propose a 4-parameter model for the fundamental frequency evolution on the whole tessitura, taking into account the model of the inhamonicity coefficient. The global model is applied to 5 different pianos (4 grand pianos and
Download Detecting arrivals within room impulse responses using matching pursuit This paper proposes to use Matching Pursuit, in order to investigate some statistical foundations of Room Acoustics, such as the temporal distribution of arrivals, and the estimation of mixing time. As this has never been experimentally explored, this study is a first step towards a validation of the ergodic theory of reverberation. The use of Matching Pursuit is implicit, since correlation between the impulse response and the direct sound is assumed. The compensation for the energy decay is necessary to obtain stationnary signals. Methods for determining the best the temporal boundaries of the direct sound, for choosing an appropriate stopping criteria based on the similarity between acoustical indices of the original RIR and those of the synthesized signal, and for experimentally defining the mixing time constitute the scope of this study.
Download Low bit-rate audio coding with hybrid representations We present a general audio coder based on a structural decomposition : the signal is expanded into three features : its harmonic part, the transients and the remaining part (referred as the noise). The rst two of these layers can be very e ciently encoded in a wellchosen basis. The noise is by construction modelized as a gaussian (colored) random noise. Furthermore, this decomposition allows a good time-frequency psycoacoustic modeling, as it dircetly provides us with the tonal and nontonal part of the signal.
Download Sparse and Structured Decompositions of Audio Signals in Overcomplete Spaces We investigate the notion of “sparse decompositions” of audio signals in overcomplete spaces, ie when the number of basis functions is greater than the number of signal samples. We show that, with a low degree of overcompleteness (typically 2 or 3 times), it is possible to get good approximation of the signal that are sparse, provided that some “structural” information is taken into account, ie the localization of significant coefficients that appears to form clusters. This is illustrated with decompositions on a union of local cosines (MDCT) and discrete wavelets (DWT), that are shown to perform well on percussive signals, a class of signals that is difficult to sparsely represent on pure (local) Fourier bases. Finally, the obtained clusters of individuals atoms are shown to carry higher levels of information, such as a parametrization of partials or attacks, and this is potentially useful in an information retrieval context.
Download Object Coding of Harmonic Sounds Using Sparse and Structured Representations Object coding allows audio compression at extremely low bit-rates, provided that the objects are correctly modelled and identified. In this study, a codec has been implemented on the basis of a sparse decomposition of the signal with a dictionary of InstrumentSpecific Harmonic atoms. The decomposition algorithm extracts “molecules” i.e. linear combinations of such atoms, considered as note-like objects. Thus, they can be coded efficiently using notespecific strategies. For signals containing only harmonic sounds, the obtained bitrates are very low, typically around 2 kbs, and informal listening tests against a standard sinusoidal coder show promising performances.
Download Inverting dynamics compression with minimal side information Dynamics processing is a widespread technique, both at music production and diffusion stages. In particular, dynamic compression is often used in such a way that the “average” listener can best enjoy the music. However, this may lead to an excessive use of compression, especially with respect to listeners in quiet listening conditions. This paper presents estimates on the amount of extra data that is needed to invert the effects of such non-linear processing, using simple blind identification techniques. We present two simple test cases, first in the case when perfect reconstruction is needed, and second when the ancillary data rate is constrained, leading to an approximate reconstruction.
Download The DESAM Toolbox: Spectral Analysis of Musical Audio In this paper is presented the DESAM Toolbox, a set of Matlab functions dedicated to the estimation of widely used spectral models for music signals. Although those models can be used in Music Information Retrieval (MIR) tasks, the core functions of the toolbox do not focus on any specific application. It is rather aimed at providing a range of state-of-the-art signal processing tools that decompose music files according to different signal models, giving rise to different “mid-level” representations. After motivating the need for such a toolbox, this paper offers an overview of the overall organization of the toolbox, and describes all available functionalities.