International conferences, workshops
| A. Novak et al. (2016), "Non-linear Identification Of An Electric Guitar Pickup", Proc. of the 16th Int. Conference on Digital Audio Effects (DAFx-16). [Abstract] [BibTeX][PDF] |
| Abstract: Physical models of electric guitars are still not very widespread in the scientific literature. Especially, the description of the non linear behavior of pickups still requires some refinements. This paper deals with the identification of pickup non linearities based on a Hammerstein representation, by means of a specific experimental set-up to drive the pickup in a controlled way. A comparison with experimental results shows that the model succeeds in describing the pickup when used in realistic conditions. |
BibTeX:@inproceedings{novak_dafx16,
author={Novak, A. and Guadagnin, L. and Lihoreau, B. and Lotton, P. and Brasseur, E. and Simon, L.},
title={Non-linear Identification Of An Electric Guitar Pickup},
booktitle={Proc. of the 16th Int. Conference on Digital Audio Effects (DAFx-16)},
year={2016},
organization={}
} |
| A. Novak, L. Simon & P. Lotton (2016), "Extension of Generalized Hammerstein Model to Non-Polynomial Inputs", EUSIPCO 2016. [Abstract] [BibTeX][PDF] |
| Abstract: The Generalized Hammerstein model has been successfully used during last few years in many physical applications to describe the behavior of a nonlinear system under test. The main advantage of such a nonlinear model is its capability to model efficiently nonlinear systems while keeping the computational cost low. On the other hand, this model can not predict complicated nonlinear behaviors such as hysteretic one. In this paper, we propose an extension of the Generalized Hammerstein model to a model with non polynomial nonlinear inputs that allows modeling more complicated nonlinear systems. A simulation provided in this paper shows a good agreement between the model and the hysteretic nonlinear system under test. |
BibTeX:@inproceedings{novak2016extension,
author={Novak, Antonin and Simon, Laurent and Lotton, Pierrick},
title={Extension of Generalized Hammerstein Model to Non-Polynomial Inputs},
booktitle={EUSIPCO 2016},
year={2016},
organization={}
} |
| E. Brasseur, A. Novak, P. Lotton, B. Lihoreau & a. L. (2016), "Développement de bancs de mesure pour la caractérisation des pickups électromagnétiques", 13e Congrès Français d'Acoustique. [Abstract] [BibTeX] |
| Abstract: Les microphones (pickups) de guitares électriques sont des transducteurs électromagnétiques sensibles à la vitesse des cordes de la guitare. Dans le cadre des recherches menées au LAUM concernant la caractérisation de ces capteurs, un premier banc de mesure a été développé. Ce banc permet de mesurer simultanément la tension de sortie du pickup et la vitesse d’une corde, lorsque celle-ci est soumise à une excitation impulsionnelle effectuée à l'aide d'un plectre automatisé. Un deuxième dispositif expérimental a été développé permettant de mesurer la réponse du pickup lorsqu’une portion de corde, montée sur un pot vibrant et placée devant le capteur, est soumise à un mouvement sinusoïdal entretenu contrôlé en fréquence et en amplitude. Le comportement du pot-vibrant étant non-linéaire, la vitesse de la corde est distordue, ce qui introduit des erreurs non négligeables dans l’analyse des résultats expérimentaux. Par conséquent un système de contrôle actif a été développé qui consiste à ajouter, en temps réel, à la tension d'excitation du pot vibrant des harmoniques supérieurs, contrôlés en amplitude et en phase de manière à générer une vitesse de la corde purement sinusoïdale. Afin de maîtriser au mieux les paramètres des pickups à caractériser, l’étude est menée sur une série de pickups monoplots réalisés au laboratoire. Les différentes étapes de conception des bancs de mesures, les contraintes techniques, les choix technologiques ainsi que le processus de réalisation des pickups seront présentés. La présentation du système de contrôle actif permettant la linéarisation de la vitesse générée par la source du deuxième banc de mesure fera l'objet d'un point particulier. |
BibTeX:@inproceedings{novakCFA16_01,
author={Brasseur, E. and Novak, A. and Lotton, P. and Lihoreau, B. and Guadagnin L.},
title={Développement de bancs de mesure pour la caractérisation des pickups électromagnétiques},
booktitle={13e Congrès Français d'Acoustique},
year={2016},
organization={}
} |
| A. Novak, P. Honzik, M. Bruneau & N. Joly (2016), "Modélisation analytique et contrôle numérique du comportement d'une micro-poutre vibrante chargée par une couche de fluide à l'arrière", 13e Congrès Français d'Acoustique. [Abstract] [BibTeX] |
| Abstract: L'usage de systèmes dynamiques miniatures (MEMS), actifs (récepteurs ou émetteurs) ou passifs, pour de nouvelles applications (audition, méta-matériaux, biens de consommations, ...) ou en métrologie sous des conditions non-standard, apparaît à l'heure actuelle dans divers domaines de l'acoustique. Des caractérisations plus précises que celles disponibles aujourd'hui sont rendues nécessaires. Dans ce contexte, le travail présenté ici porte sur une approche analytique et numérique pour décrire le comportement des diverses formes de systèmes comportant chacun une micro-poutre de forme rectangulaire (poutre rigide suspendue ou poutre élastique plane) chargée à l'arrière par une petite cavité ou une fine couche de fluide, entourée de très fines fentes (qui évitent la conception complexe de suspensions, assurent l'équilibre des pressions statiques et contribuent à l'amortissement), et mise en vibration par un champ acoustique incident. La modélisation analytique prend en compte le fort couplage entre la poutre et le champ de pression acoustique à l'arrière, les processus de diffusion visqueux et thermiques dans les couches limites dans les fentes et la cavité arrière, le comportement modal dans le cas de la poutre élastique, la non uniformité du champ acoustique à l'arrière de la poutre qui est modélisée en faisant usage du formalisme intégral, et finalement le couplage des champs acoustiques de part et d'autre de la poutre au travers des fentes. Dans les diverses configurations étudiées, des solutions générales sont proposées pour le mouvement de la poutre, conduisant à exprimer une sensibilité, une impédance d'entrée ou une fonction de transfert acoustique selon le système considéré en pratique. Un calcul numérique (FEM) est mené en parallèle, qui permet de valider les résultats analytiques obtenus. |
BibTeX:@inproceedings{novakCFA16_02,
author={Novak, A. and Honzik, P. and Bruneau, M. and Joly, N.},
title={Modélisation analytique et contrôle numérique du comportement d'une micro-poutre vibrante chargée par une couche de fluide à l'arrière},
booktitle={13e Congrès Français d'Acoustique},
year={2016},
organization={}
} |
| A. Novak, P. Honzik, M. Bruneau & F. Fohr (2016), "Étude de filtre pour protecteur auditif passif", 13e Congrès Français d'Acoustique. [Abstract] [BibTeX] |
| Abstract: Les protecteurs auditifs passifs placés dans le canal auditif sont d'usage courant pour assurer la protection contre les bruits intenses. De nos jours, les différents principes utilisés permettent généralement de réaliser des atténuations globales de 15 dB à 25 dB mais avec une courbe de restitution en fréquence très déséquilibrée (atténuation principalement des hautes fréquences et suppression de la résonance naturelle du canal auditif vers 3 kHz). Seuls les principes de filtres acoustiques utilisant une fine membrane fermant le canal présentent une réponse en fréquence plus équilibrée. Cependant, ce principe présente l'inconvénient majeur d’empêcher la ventilation du canal auditif (transpiration) et l'égalisation de pression. Pour tenter de proposer une autre voie de développement de filtres acoustiques à réponse en fréquence adaptée, nous proposons une étude qui a pour objet d'associer des petits éléments dont le comportement relève des fonctions de petits guides et cavités de formes adaptées, couplés entre eux, formant ainsi un système qui ne nécessite pas l'usage de membrane (tout au plus celui d'un petit oscillateur). Les résultats analytiques et numériques obtenus à ce jour, qui prennent en compte la dissipation thermo-visqueuse dans les couches limites, montrent la faisabilité de tels protecteurs auditifs. |
BibTeX:@inproceedings{novakCFA16_03,
author={Novak, A. and Honzik, P. and Bruneau, M. and Fohr, F.},
title={Étude de filtre pour protecteur auditif passif},
booktitle={13e Congrès Français d'Acoustique},
year={2016},
organization={}
} |
| B. Maillou, P. Lotton, A. Novak & L. Simon (2016), "Comportement Non-Linéaire des Suspensions Mécaniques d'un Haut-Parleur : Caractérisation et Identification", 13e Congrès Français d'Acoustique. [Abstract] [BibTeX] |
| Abstract: Dans le fonctionnement d'un haut-parleur électrodynamique, les non-linéarités générées en cas de fort niveau d'excitation électrique peuvent être d'origines électrique, mécanique ou acoustique. Le travail présenté ici porte sur le comportement mécanique en basses fréquences de l'équipage mobile lorsqu'il est soumis à un déplacement de grande amplitude, et plus spécifiquement sur le comportement des suspensions. Traditionnellement, le modèle de Thiele & Small décrit le comportement mécanique de l'équipage mobile en régime linéaire comme celui d'un système masse-ressort amorti. En régime non-linéaire, les paramètres de raideur et d'amortissement de ce modèle ne suffisent plus pour décrire le comportement mécanique complexe observé. L'identification d'un modèle « Hammerstein Généralisé », à partir de données expérimentales caractérisant un équipage mobile d'un haut-parleur découplé de la partie "moteur magnétique", est alors proposée. Les performances et limites d'un tel modèle non-linéaire non-paramétrique des suspensions de haut-parleur sont discutées. Enfin, les paramètres d’un modèle dit de « Thiele et Small étendu » sont déduits à partir des paramètres du modèle «Hammerstein Généralisé» et permettent de mettre en évidence l’évolution de la raideur et de l’amortissement avec la fréquence d’excitation et le déplacement de la membrane, ainsi que la dépendance des phénomènes observés avec le niveau d’excitation. |
BibTeX:@inproceedings{novakCFA16_04,
author={Maillou, B. and Lotton, P. and Novak, A. and Simon, L.},
title={Comportement Non-Linéaire des Suspensions Mécaniques d'un Haut-Parleur : Caractérisation et Identification},
booktitle={13e Congrès Français d'Acoustique},
year={2016},
organization={}
} |
| B. Maillou, P. Lotton, A. Novak & L. Simon (2014), "Mechanical Nonlinearities of Electrodynamic Loudspeakers: An Experimental Study", Audio Engineering Society Convention 136. [Abstract] [BibTeX][URL] |
| Abstract: Spider and surround suspensions are at the origin of viscoelastic and nonlinear behaviors of loudspeakers because of their assembly geometry and their intrinsic materials. We propose here a new dynamic experimental method to characterize these properties. We drive the loudspeaker moving part with a shaker and measure the driving force, the acceleration, the velocity, and the displacement. Results are presented and discussed for a given loudspeaker, which surround suspensions exhibit viscoelastic behavior. |
BibTeX:@inproceedings{maillou2014mechanical,
author={Maillou, Balbine and Lotton, Pierrick and Novak, Antonin and Simon, Laurent},
title={Mechanical Nonlinearities of Electrodynamic Loudspeakers: An Experimental Study},
booktitle={Audio Engineering Society Convention 136},
year={2014},
organization={Audio Engineering Society}
} |
| A. Novak, P. Lotton & L. Simon (2014), "Dynamic measurement of loudspeaker suspension parameters using an active harmonic control technique", Audio Engineering Society Convention 136. [Abstract] [BibTeX][URL] |
| Abstract: A new nondestructive technique to measure the nonlinear suspension parameters (stiffness Kms and mechanical resistance Rms) of a loudspeaker using an active harmonic control technique is presented. The goal of the active harmonic control is to eliminate the higher harmonics from the displacement signal so that a purely harmonic motion of the diaphragm is ensured. The nonlinear stiffness Kms is then measured as a function of instantaneous and peak displacement; the mechanical resistance Rms is measured as a function of velocity. A frequency dependence of these parameters is also discussed. |
BibTeX:@inproceedings{novak2014dynamic,
author={Novak, Antonin and Lotton, Pierrick and Simon, Laurent},
title={Dynamic measurement of loudspeaker suspension parameters using an active harmonic control technique},
booktitle={Audio Engineering Society Convention 136},
year={2014},
organization={Audio Engineering Society}
} |
| A. Novak, P. Lotton & L. Simon (2014), "Nonlinear Force Factor Measurement of an Electrodynamic Loudspeaker", Proc. Forum Acusticum. [Abstract] [BibTeX][PDF][URL] |
| Abstract: An electrodynamic loudspeaker is usually characterized using a linear lumped parameter model, whose physical parameters are assumed to be constant. Such a linear approximation is sufficient for small excitation levels, but becomes insufficient for larger ones. The model is therefore usually extended allowing a variation of the parameters with the displacement of the diaphragm, the current intensity in the coil, the frequency and many other physical quantities. One of the important nonlinear parameters is the force factor Bl that characterizes the magneto-electrical performance of the loudspeaker and that can be highly dependent on the voice-coil displacement. In this paper, we propose a simple and precise method to estimate the force factor Bl of the loudspeaker as a function of the displacement of the voice-coil. The voice-coil is displaced from its rest position electrically using a direct current and a swept-sine signal of small level is fed to the loudspeaker. The signals of the electric tension, the current and the velocity of the diaphragm are recorded and used to estimated the force factor Bl. This process is repeated with different values of direct current to obtain the force factor as a static function of the voice-coil displacement. The experimental results of arbitrary chosen loudspeakers are shown.
|
BibTeX:@inproceedings{novak2014force,
author={Novak, Antonin and Lotton, Pierrick and Simon, Laurent},
title={Nonlinear Force Factor Measurement of an Electrodynamic Loudspeaker},
booktitle={Proc. Forum Acusticum},
year={2014},
organization={EAA}
} |
| B. Maillou et al. (2012), "Electrodynamic loudspeakers suspensions nonlinearities, study and measurements", Acoustics 2012 Nantes. [Abstract] [BibTeX][URL] |
| Abstract: Nonlinearities characterization and identification of acoustical systems is an active research field, notably in the area of electroacoustics. An innovative characterization and identification method, based on the nonlinear convolution and the use of a synchronized swept-sine excitation signal, has recently been developped. In this paper, this method is applied to the study of the nonlinearities exhibited by the mechanical suspensions of an electrodynamic loudspeaker. Nonlinear behaviours are specially studied as function of the amplitude of the displacement of the membrane of the loudspeaker. In this context, we develop an experimental setup from the signal generator to the mobile part of the tested component, specially designed in order to obtain a great harmonic distortion measurement dynamic range and, thus, to allow the measurement of weak nonlinearities. Nonlinearities are estimated for both the external and internal suspensions independently, and for several kinds of loudspeakers. Results are compared with those obtained by other methods available in the literature. |
BibTeX:@inproceedings{maillou2012electrodynamic,
author={Maillou, Balbine and Novak, Antonin and Blondeau, James and Brouard, Bruno and Génevaux, Jean-Michel and Lotton, Pierrick and Simon, Laurent},
title={Electrodynamic loudspeakers suspensions nonlinearities, study and measurements},
booktitle={Acoustics 2012 Nantes},
year={2012},
organization={}
} |
| A. Novak & B. Merit (2012), "Magnet-only loudspeaker motors: linear behavior theory vs. Nonlinear measurements", Acoustics 2012 Nantes. [Abstract] [BibTeX][PDF][URL] |
| Abstract: A few years ago, a new concept of magnet-only loudspeaker has been proposed to improve the quality of the reproduced sound. Such a loudspeaker is called magnet-only because its magnetic circuit is totally made of rare-earth permanent magnets. Unlike the classical electrodynamic loudspeaker, no iron is used. According to the theory, the exclusive use of permanent magnets and the absence of iron can lead to a uniform motor parameters (force factor Bl, resistance Re and inductance Le) over the voice-coil displacement and thus to a decrease of the nonlinear distortion and to an improvement of the sound quality. To our knowledge, such motor parameters have not been consistently quantified, neither their variations. In this paper, the variation of the parameters of a magnet-only loudspeaker are measured. The goal is to verify the theory and to show that using a simple measurement procedure one can understand better why a magnet-only loudspeaker improves the quality of the reproduced sound. |
BibTeX:@inproceedings{novak2012magnet,
author={Novak, Antonin and Merit, Benoit},
title={Magnet-only loudspeaker motors: linear behavior theory vs. Nonlinear measurements},
booktitle={Acoustics 2012 Nantes},
year={2012},
organization={}
} |
| A. Novak & B. Merit (2012), "Static and Dynamic Measurement of a Magnet-only Loudspeaker", EURONOISE 2012. [Abstract] [BibTeX][PDF] |
| Abstract: A new loudspeaker technology using Magnet-only motors has been presented recently. Unlike the classical electrodynamic loudspeaker, no iron is used in the motor part. The presence of iron in traditional loudspeaker motor is a source of nonlinearities and, as a consequence, deteriorates the reproduced sound quality. According to the theory of Magnet-only motors, the loudspeaker parameters should vary less than in the case of a classical electrodynamic loudspeaker. In this paper, the parameters of a Magnet-only loudspeaker are measured statically and dynamically. The results presented in this paper clarify why a magnet-only loudspeaker improves the quality of the reproduced sound. |
BibTeX:@inproceedings{novak2012euronoise,
author={Novak, Antonin and Merit, Benoit},
title={Static and Dynamic Measurement of a Magnet-only Loudspeaker},
booktitle={EURONOISE 2012},
year={2012},
organization={EURONOISE}
} |
| P. Michaud, P. Herzog, S. Meunier & A. Novak (2011), "Perceptual evaluation of loudspeaker nonlinearities", Proc. Forum Acusticum. [Abstract] [BibTeX][PDF][URL] |
| Abstract: This study deals with the evaluation of the perception of distortion in the restitution of musical excerpts played by loudspeakers. The main focus is to evaluate the perceived distortion induced by low frequency nonlinearities of the loudspeaker. A large panel is created in which only the distortion varies among the loudspeakers. The "virtual" loudspeakers are created from one single actual loudspeaker by associating its anechoic filtered tweeter recording and its woofer signal model in which the distortion can be modified. To model the woofer restitution, its identification is done using a swept sine technique which separates the linear and higher order impulse responses. These impulse responses are used as linear and nonlinear frequency filters characterizing the sound pressure of the system under test. The woofer synthesis consists in expanding the musical excerpts on the basis of Chebyshev polynomials combined with the identified frequency filters (Novak et al., DAFx 2010). Different "virtual" loudspeakers are obtained by amplifying or reducing the influence of specific nonlinearities. In order to evaluate the perceived distortion, in realistic listening conditions, the auralization technique was used to convolve the "virtual" loudspeakers with the impulse response of a suitable room. Upcoming listening tests are conducted with headphones to evaluate the perceived differences over the created panel of loudspeakers with a method allowing the evaluation of large sets of stimuli. The dissimilarity judgments can then be analyzed with a Multidimensional scaling (MDS) technique to reveal the underlying dimensions of the distortion space. |
BibTeX:@inproceedings{michaud2011perceptual,
author={Michaud, Pierre-Yohan and Herzog, Philippe and Meunier, Sabine and Novak, Antonin},
title={Perceptual evaluation of loudspeaker nonlinearities},
booktitle={Proc. Forum Acusticum},
year={2011},
organization={}
} |
| A. Novak, L. Simon, P. and Lotton & J. Gilbert (2010), "Chebyshev Model and Synchronized Swept Sine Method in Nonlinear Audio Effect Modeling", Proc. of the 13th Int. Conference on Digital Audio Effects (DAFx-10). [Abstract] [BibTeX][PDF][URL] |
| Abstract: A new method for the identification of nonlinear systems, based on an input exponential swept sine signal has been proposed by Farina ten years ago. This method has been recently modified in purpose of nonlinear model estimation using a synchronized swept sine signal. It allows a robust and fast one-path analysis and identification of the unknown nonlinear system under test. In this paper this modified method is applied with Chebyshev polynomial decomposition. The combination of the Synchronized Swept Sine Method and Chebyshev polynomials leads to a nonlinear model consisting of several parallel branches, each branch containing a nonlinear Chebyshev polynomial following by a linear filter. The method is tested on an overdrive effect pedal to simulate an analog nonlinear effect in digital domain. |
BibTeX:@inproceedings{novak_dafx10,
author={Novak, A. and Simon, L. and and Lotton, P and Gilbert, J.},
title={Chebyshev Model and Synchronized Swept Sine Method in Nonlinear Audio Effect Modeling},
booktitle={Proc. of the 13th Int. Conference on Digital Audio Effects (DAFx-10)},
year={2010},
organization={}
} |
| F. Kadlec, K. Ulovec & A. Novak (2010), "Application of SWT and MISO Methods for Measurement and Analysis of Electro-Acoustic and Audio Systems", 17th Internation congress on Sound and Vibration. [Abstract] [BibTeX][PDF][URL] |
| Abstract: This contribution deals with performance evaluation of electro-acoustic and audio systems with non-linearities by a combination of two existing methods: Sweep Sine Wave Signal Technique (SWT) and Multiple Input Single Output (MISO) nonlinear modeling. The signal, driving a system under test, is a logarithmically swept sine wave. Transfer functions of the system under test may be obtained from the response of the system and the swept sine wave "inverse filter" response. These transfer functions are further processed. Then the system under test can be considered as a MISO nonlinear model, consisting of a parallel combination of nonlinear branches, containing filters and memory-less power-law distortion functions. Such a model facilitates determination of a nonlinear response to the input signal. This method has been successfully used for analysis of various components of electro-acoustic and audio systems. In the first application described in our contribution, this method was used for a detailed analysis of transfer functions of a complete electro-acoustic system including an artificial head. This system is used for the analysis of spatial perception as well as determination of a signal compression impact on its perception. In the other application, this test method was used for measurement and evaluation of the whole transmission chain, from studio all the way to the listener. The signal source was a studio recorded CD that was transmitted by FM radio to the listener's receiver, where it was demodulated, monitored and analyzed. A good correlation with traditional methods of measurement was found. |
BibTeX:@inproceedings{icsv17,
author={Kadlec, F. and Ulovec, K. and Novak, A.},
title={Application of SWT and MISO Methods for Measurement and Analysis of Electro-Acoustic and Audio Systems},
booktitle={17th Internation congress on Sound and Vibration},
year={2010},
organization={}
} |
| A. Novak, M. Bentahar, V. Tournat, R. El Guerjouma & L. Simon (2010), "Strutural Health Monitoring Based on Nonlinear System Identification", 10th French Congress of Acoustics. [Abstract] [BibTeX][URL] |
| Abstract: In classical nonlinear resonance experiments, we generally use of a gain/phase analyzer to excite and display the materials Frequency Response Function FRF. However, the latter response is obtained using a tracking filter around the fundamental excitation frequency. In that case, the obtained information is generally a combination of the desired response and a contribution of a power series of harmonics responses. Moreover, the filtering procedure prevents from having higher harmonics responses whose knowledge is important in nonlinear damage characterization. In this contribution we propose a nonlinear system identification method based on an exponential swept-sine drive signal. The recorded response of the material under test is convolved with an inverse filter to obtain the nonlinear responses corresponding to the harmonics usually eliminated by the gain/phase analyzer filtering system. Therefore, a single swept-sine experiment allows to estimate higher harmonics responses (amplitude and phase) depending on the nonlinear behaviour of the material. The first measurements performed on a damaged polymer-based composite reveal that higher harmonics, generally neglected in nonlinear damage characterization because of the tracking filter, are very sensitive to damage and hence deserve more attention than usual. As the sensors stand by the structure this method could be used advantageously in Structural Health Monitoring. |
BibTeX:@inproceedings{CFA10_02,
author={Novak, A. and Bentahar, M. and Tournat, V. and El Guerjouma, R. and Simon, L.},
title={Strutural Health Monitoring Based on Nonlinear System Identification},
booktitle={10th French Congress of Acoustics},
year={2010},
organization={}
} |
| A. Novak, L. Simon, P. Lotton & J. Gilbert (2010), "Nonlinear Analysis and Modeling of Electrodynamic Loudspeakers Based on Exponential Swept Sine Input Signal", 10th French Congress of Acoustics. [Abstract] [BibTeX][PDF][URL] |
| Abstract: Many real-world systems exhibit nonlinear behavior that must be taken into account when modeling such systems. In practise, especially in the field of electro-acoustics, nonlinearities appear with increasing input level. These nonlinearities are usually modeled by adding nonlinear parameters to the linear model, but the determination of nonlinear physical parameters is rather difficult problem. The authors present a simple method for analysis and identification of nonlinear systems, based on swept-sine signal excitation. The method is based on nonlinear convolution, firstly proposed by Angelo Farina [1], which serves for analysis of nonlinear amplitude characteristics. The result of the nonlinear convolution method is the set of harmonic distortion products (higher order nonlinear impulse responses) that can be expressed either in the form of the separated impulse responses or in the form of frequency dependent components. The original method [1] was improved in order to analyze also the phase charceristics of all the nonlinear parts. Therefore, the excitation sweep signal from the improved method [2] has to be setup very properly. The precisely measured nonlinear amplitude and phase characteristics can be used for analysis of the nonlinear system under test, or for identification of a nonlinear model (i.e. generalized Hammerstein model). The method is presented here when studying an electrodynamic loudspeaker from the nonlinear point of view. More precisely the electrodynamic loudspeaker under test is characterized by its electrical impedance leading to Thiele/Small parameters in a nonlinear framework.
[1] A. Farina, ''Simultaneous measurement of impulse response and distortion with a swept-sine technique'', in Proc. 108th AES Convention, Paris, February, 2000.
[2] A. Novak et al., ''Nonlinear System Identification Using Exponential Swept Sine Signal'', accepted for publication in IEEE Instrumentation and Measurement, 2009 |
BibTeX:@inproceedings{CFA10_01,
author={Novak, A. and Simon, L. and Lotton, P. and Gilbert, J.},
title={Nonlinear Analysis and Modeling of Electrodynamic Loudspeakers Based on Exponential Swept Sine Input Signal},
booktitle={10th French Congress of Acoustics},
year={2010},
organization={}
} |
| A. Novak, M. Bentahar, V. Tournat, R. El Guerjouma & L. Simon (2010), "Can nonlinear convolution improve damage characterization using acoustic methods ?", 5eme Colloque Interdisciplinaire en Instrumentation. [Abstract] [BibTeX][PDF] |
| Abstract: This work presents an original damage characterisation method of homogeneous and heterogeneous solids using a signal processing-based experimental approach. Convolution nonlinear method is used in order to improve experimental observations allowing to measure simultaneously the well known vibration spectrum, classically found using analysers, and harmonic spectrums which are out of reach when using the same analysers. The experimental approach has been validated to characterise a progressive damage corresponding to materials of different shape and nature (glass beads, polymer-based composite plates). |
BibTeX:@inproceedings{C2I,
author={Novak, A. and Bentahar, M. and Tournat, V. and El Guerjouma, R. and Simon, L.},
title={Can nonlinear convolution improve damage characterization using acoustic methods ?},
booktitle={5eme Colloque Interdisciplinaire en Instrumentation},
year={2010},
organization={}
} |
| A. Novak, L. Simon, F. Kadlec & P. Lotton (2009), "Modeling of Nonlinear Audio Systems using Swept-Sine signals: Application to audio effects", Proc. of the 12th Int. Conference on Digital Audio Effects (DAFx-09). [Abstract] [BibTeX][PDF][URL] |
| Abstract: In this paper a new method for analysis and modeling of nonlinear audio
systems is presented. The method is based on swept-sine excitation signal and nonlinear
convolution firstly presented in [1, 2]. It can be used in nonlinear processing for audio
applications, to simulate analog nonlinear effects (distortion effects, limiters) in digital
domain. |
BibTeX:@inproceedings{novak2009modeling,
author={Novak, A. and Simon, L. and Kadlec, F. and Lotton, P},
title={Modeling of Nonlinear Audio Systems using Swept-Sine signals: Application to audio effects},
booktitle={Proc. of the 12th Int. Conference on Digital Audio Effects (DAFx-09)},
year={2009},
organization={}
} |
| Novak A., Bentahar B., Tournat V., Simon L. & (2009), "Sensitive Damage Characterization Based on Nonlinear System Identification", ICNEW XIV. [BibTeX][URL] |
| Abstract: |
BibTeX:@inproceedings{ICNEW,
author={Novak A., and Bentahar B., and Tournat V., and Simon L., and El Guerjouma R.},
title={Sensitive Damage Characterization Based on Nonlinear System Identification},
booktitle={ICNEW XIV},
year={2009},
organization={}
} |
| F. Kadlec & A. Novak (2008), "Measurement and Analysis of Non-linear Distortion of Electro-acoustic and Audio Systems", 15th Internation congress on Sound and Vibration. [Abstract] [BibTeX][PDF][URL] |
| Abstract: A novel technique for analysis of nonlinear distortion of electro-acoustic and audio systems is presented. The method is based on the combination of a Sweep sine Wave signal Technique (SWT) and a Multiple Input Single Output (MISO) nonlinear modeling. The signal driving a system under test is a logarithmic sine wave sweep. The response of the system under test is acquired and used in a convolution with swept sine wave "inverse filter" response to obtain a set of transfer functions. This set of transfer functions provides information about harmonic distortion. These transfer functions are further processed. Then the system under test can be modeled as a MISO nonlinear model, consisting of a parallel combination of nonlinear branches containing filters and memory-less power-law distortion functions. Such a model facilitates determination of a nonlinear response to the input signal. This method was used to analyze transfer functions of various components of electro-acoustic systems. It was applied to testing of recording and reproduction equipment for audio signals, including equipment for their further digital signal processing. During testing of multichannel systems, the method enables evaluation of not only individual channels, but also their mutual interaction. A good correlation with traditional methods of distortion measurement has been shown. |
BibTeX:@inproceedings{ICSV15,
author={Kadlec, F. and Novak, A.},
title={Measurement and Analysis of Non-linear Distortion of Electro-acoustic and Audio Systems},
booktitle={15th Internation congress on Sound and Vibration},
year={2008},
organization={}
} |
| A. Novak, L. Simon, J. Gilbert, P. Lotton & F. Kadlec (2008), "Comparison of non Linear System Identification Methods : the Example of non Linear Propagation of Acoustic Waves in Ducts", Proceedings of Acoustics'08 Paris. [Abstract] [BibTeX][URL] |
| Abstract: The weakly non linear propagation of travelling acoustic waves in ducts is a well known problem leading to approximated analytical solutions. From an experimental point of view, the classical way for estimating the non linear parameters of propagation is to generate sine waves and to analyse the higher order harmonics as a function of the amplitude and the frequency of the excitation. In this work, new methods for estimating the non linear parameters of propagation are developed and compared to the sine excitation based method. The excitation signals associated to these new methods can be stationary noise or logarithmic chirps. For these excitation signals, the data processing is based on Multiple Input Single Output (MISO) direct path method. The comparison is made in terms of signal to noise ratio robustness and computation time. Experimental and theoretical results are also compared. We particularly show that a measurement using only one logarithmic chirp allows estimating accurate results for a broad band of amplitudes and frequencies. Associated computational time is then drastically reduced. |
BibTeX:@inproceedings{Acoustics08,
author={Novak, A. and Simon, L. and Gilbert, J. and Lotton, P. and Kadlec, F.},
title={Comparison of non Linear System Identification Methods : the Example of non Linear Propagation of Acoustic Waves in Ducts},
booktitle={Proceedings of Acoustics'08 Paris},
year={2008},
organization={}
} |
| A. Novak, L. Simon, F. Kadlec & P. Lotton (2008), "A New Method for Identification of Nonlinear Systems Using MISO Model with Swept-Sine Technique: Application to Loudspeaker Analysis", 124th AES Convention. [Abstract] [BibTeX][URL] |
| Abstract: This work presents a Multiple Input Single Output (MISO) nonlinear model in combination with sine-sweep signals as a method for nonlinear system identification. The method is used for identification of loudspeaker nonlinearities and can be applied to nonlinearities of any audio components. It extends the method based on nonlinear convolution presented by Farina, providing a nonlinear model that allows to simulate the identified nonlinear system. The MISO model consists of a parallel combination of nonlinear branches containing linear filters and memory-less power-law distortion functions. Once the harmonic distortion components are identified by the method of Farina, the linear filters of the MISO model can be derived. The practical application of the method is demonstrated on a loudspeaker. |
BibTeX:@inproceedings{aes08,
author={Novak, A. and Simon, L. and Kadlec, F. and Lotton, P.},
title={A New Method for Identification of Nonlinear Systems Using MISO Model with Swept-Sine Technique: Application to Loudspeaker Analysis},
booktitle={124th AES Convention},
year={2008},
organization={}
} |
| A. Novak, F. Kadlec, L. Simon & P. Lotton (2008), "Direct Path MISO method: Identification of Nonlinear Electro-acoustic Systems", Proceedings of Workshop 2008. [BibTeX][PDF] |
| Abstract: |
BibTeX:@inproceedings{worshop08,
author={Novak, A. and Kadlec, F. and Simon, L. and Lotton, P.},
title={Direct Path MISO method: Identification of Nonlinear Electro-acoustic Systems},
booktitle={Proceedings of Workshop 2008},
year={2008},
organization={Czech Technical University in Prague}
} |
| A. Novak & F. Rund (2007), "Systematicke chyby pri analyze nelinearnich systemu", Technical Computing Prague 2007. [BibTeX][PDF][URL] |
| Abstract: |
BibTeX:@inproceedings{humsoft2007novak,
author={Novak, A. and Rund, F.},
title={Systematicke chyby pri analyze nelinearnich systemu},
booktitle={Technical Computing Prague 2007},
year={2007},
organization={}
} |
| F. Kadlec & A. Novak (2007), "Comparision of Measurements Method for Analysis Electro-acoustic Systems with Non-linearities", 19th International Congress on Acoustics. [Abstract] [BibTeX][PDF] |
| Abstract: The great level of excitation of electro-acoustic systems may cause a nonlinear distortion of signal, which has an effect on its perception. For analysing and monitoring functionality of such a system there are two methods, Multiple-Input Single-Output method for nonlinear systems and a method utilizing sweep sine wave signals, which are compared in this contribution. The first method uses a stationary Gaussian random process as the input signal. Then a nonlinear system is represented by a multiple inputs linear system and additional nonlinear inputs are determined according to decorrelated power series expansion of the main input signal. The second method uses a logarithmic sweep signal as the input signal. The impulse response of the system is obtained by a convolution of the system response to the input sweep signal and the "inverse filter". The impulse response consists of several distorted partial components. These two methods have been compared from the accuracy of the algorithmic point of view and also by measuring by an electro-acoustic system. |
BibTeX:@inproceedings{ica02,
author={Kadlec, F. and Novak, A.},
title={Comparision of Measurements Method for Analysis Electro-acoustic Systems with Non-linearities},
booktitle={19th International Congress on Acoustics},
year={2007},
organization={}
} |
| A. Novak (2007), "Identification of Nonlinearity of Electro-acoustic Systems using a Direct Path MISO Method", 19th International Congress on Acoustics. [Abstract] [BibTeX][PDF] |
| Abstract: The work deals with the Direct Path Multiple-Input Single-Output (MISO) method adapted for the identification of Nonlinearity of Electro-acoustic Systems. The method is based on a blind identification which uses decorrelated power series expansion, without having any knowledge of the shape of the nonlinear function. The nonlinear Direct Path model is represented by an equivalent Multiple-Input Single-Output linear model, where the inputs are nonlinear contributions of the original input signal. Each branch of a complex nonlinear model, with its nonlinear input, represents a "separable nonlinearity" or a static nonlinearity that is followed by a linear system so that the memory effect is represented by a linear filter. The input signal for identification is a record from stationary Gaussian random process. The method has been numerically tested on static nonlinear systems, such as limiter and death-zone systems. Also, an experiment on real electro-acoustic system has been performed. |
BibTeX:@inproceedings{ica01,
author={Novak, A.},
title={Identification of Nonlinearity of Electro-acoustic Systems using a Direct Path MISO Method},
booktitle={19th International Congress on Acoustics},
year={2007},
organization={}
} |
| A. Novak (2007), "Identification of Nonlinear Systems: MISO modeling", Poster 2007. [Abstract] [BibTeX][PDF] |
| Abstract: Abstract. In this paper, the fundamentals of analysis of nonlinear systems using the direct path MISO method (Multiple Input / Single Output ) with the input signal as a record from stationary gaussian (ergodic) random process with zero mean value will be introduced. The MISO technique for linear system is well known in many fields of science and technical applications and the first publications using MISO technique for nonlinear systems was presented by J.S.Bendat. This technique has been used in some acoustical applications (for example in vibration analysis). This paper will discuss the application of MISO method for general nonlinear system using a polynomial series. An easy experiment will be conducted to show the functionality of this method. |
BibTeX:@inproceedings{poster02,
author={Novak, A.},
title={Identification of Nonlinear Systems: MISO modeling},
booktitle={Poster 2007},
year={2007},
organization={}
} |
| A. Novak (2007), "Identification of Nonlinear Systems: Volterra Series", Poster 2007. [Abstract] [BibTeX][PDF] |
| Abstract: Traditional measurement of multimedia systems such as linear impulse response, transfer function, are sufficient but not faultless. For these methods the pure linear system is considered. Nonlinearities, which are usually included in the most of real systems are disregarded. One of the simple methods that can describe the nonlinear system used in practice is coefficient of distortion or intermodulation distortion, but these methods cannot be used to determine nonlinearities themselves. This paper describe one of the methods to identify nonlinear systems called Volterra Series. A simplification for this method is proposed and an experiment with audio amplifier is shown to test this method. |
BibTeX:@inproceedings{poster03,
author={Novak, A.},
title={Identification of Nonlinear Systems: Volterra Series},
booktitle={Poster 2007},
year={2007},
organization={}
} |
| F. Rund & A. Novak (2006), "Problem spatne synchronizace vzorkovacich kmitoctu u MLS signalu: Model v prostredi MATLAB", Technical Computing Prague 2006. [BibTeX][PDF] |
| Abstract: |
BibTeX:@inproceedings{humsoft06,
author={Rund, F. and Novak, A.},
title={Problem spatne synchronizace vzorkovacich kmitoctu u MLS signalu: Model v prostredi MATLAB},
booktitle={Technical Computing Prague 2006},
year={2006},
organization={}
} |
| A. Novak (2006), "Digital Loudspeaker Arrays Analysis", Poster 2006. [Abstract] [BibTeX][PDF] |
| Abstract: This paper deals with the properties of loudspeaker with direct digital to analog conversion, the basic goal being to replace D/A converter , amplifier , and classic speakers. The advantages of this system should be lower operating costs and greater applicability. The main part of this paper is aimed at analyzing the signals acquired from the theoretical model of the digital loudspeaker arrays (DLA) with regards to the arangement of elements on the transducer field and the point of observation. |
BibTeX:@inproceedings{poster01,
author={Novak, A.},
title={Digital Loudspeaker Arrays Analysis},
booktitle={Poster 2006},
year={2006},
organization={}
} |
