Nacer Hamzaoui - Academia.edu (original) (raw)

Papers by Nacer Hamzaoui

Research paper thumbnail of Experimental Study of Real Gear Transmission Defects Using Sound Perception

Lecture notes in mechanical engineering, Sep 1, 2016

Research paper thumbnail of Localisation de l'excitation à partir de la déformée d'une poutre en utilisant les réseaux de neurones

HAL (Le Centre pour la Communication Scientifique Directe), Mar 23, 2005

Research paper thumbnail of Détection des défauts mécaniques par réseaux de neurones, Analyse sur banc d'essai expérimental

HAL (Le Centre pour la Communication Scientifique Directe), 2008

Research paper thumbnail of Detection mechanical defects by neural networks. Experimental analysis

HAL (Le Centre pour la Communication Scientifique Directe), 2012

Research paper thumbnail of Evaluation des indicateurs de surveillance par analyse vibratoire : Application aux engrenages et roulements

In this paper, we evaluate several criteria of vibration analysis signal in the temporal field. T... more In this paper, we evaluate several criteria of vibration analysis signal in the temporal field. The objective is to evaluate their ability to detect a single or multiple fault, their ability to evaluate the severity of a bearing fault, and their ability to detect sound gearing or faulty gearing in different fault configurations created on the gear and bearing mounted on an experimental test stand. In order to evaluate the robustness of each criterion, operating parameters of the machines are taking into account in the experimental design to carry out tests under various conditions of use of the machine. We take into account parameters such as speed and load that we experiment different values to determine their influences on the criteria studied. If we identify the criterion under these conditions, then it is very likely that this is the appropriate criterion to detect the type of defect involved.

Research paper thumbnail of Detection of rolling bearing defects using discrete wavelet analysis

Meccanica, Nov 29, 2007

In the detection of bearing faults the so much desired objective remains the extraction of the de... more In the detection of bearing faults the so much desired objective remains the extraction of the defect vibratory signature from the measured signal in which immerses the random noise and other components of the machine. In this article a denoising method of the measured signals is presented. Based on the optimization of wavelet multiresolution analysis, it uses the kurtosis as an optimization and evaluation criterion, several parameters were then selected. The experimental results show the validity of this method within the detection of several defects simulated on ball bearings. The various configurations, in which the signals were measured, allow leading to optimum conditions of its application. The application of WMRA on filtered signals allows better results than its application on wide bands signals or a simple band pass filtering.

Research paper thumbnail of Comparative study between objective and subjective methods for identifying the gravity of single and multiple gear defects in case of noisy signals

Applied Acoustics, 2022

Abstract This paper aims to compare two approaches for the identification of gear defects in a ve... more Abstract This paper aims to compare two approaches for the identification of gear defects in a very noisy environment. The first one, called subjective, is based on sound perception using paired comparison test; the second, objective, is based on vibration analysis using three advanced signal processing methods. The first part of the paper determines a correlation between the sound perception obtained by the listeners and the scalar indicators calculated for different gravities of gear defects (simple and/or double). The perception test was carried out on sounds obtained directly by converting the measured vibratory signals. The study is conducted in a two-dimensional proximity space. The results obtained allowed the determination of mathematical models that correlate between the objective and subjective aspects and highlight the important relationship between the vibratory indicators and the distances between the sounds in the perceptual space. The correlation ratios obtained for the first dimension (DIM1) prove to be very significant. In the second part of the paper, the same signals are processed by three methods, known to be powerful tools in vibratory signal processing, namely Optimized Wavelet Multi-Resolution Analysis (WMRA), cyclostationary analysis, and a hybrid approach based on an improved version of the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) and multivariate denoising by wavelets and PCA (Principal Component Analysis). For all three methods considered, a demodulation approach is performed to obtain an envelope spectrum as a final result. In the case of very noisy signals, the subjective method allows a better assessment of the evolution of the severity of the gear defects compared to the objective methods used. In our opinion, this is due to the high sensitivity of the human ear to identify the existence of a defect and to assess its degree of severity, far better than the most sophisticated objective signal processing methods, which remain limited in the case of very noisy signals.

Research paper thumbnail of Optimisation de l'analyse statistique des signaux vibratoires induits par des roulements défectueux

HAL (Le Centre pour la Communication Scientifique Directe), 2007

Research paper thumbnail of Perceptual Study of Simple and Combined Gear Defects

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2017

Research paper thumbnail of Optimisation de l'analyse multirésolution en ondelettes pour la détection précoce des défauts de roulements

HAL (Le Centre pour la Communication Scientifique Directe), 2006

-L'objectif de cet article est de proposer l'analyse multirésolution en ondelettes en tant qu'out... more -L'objectif de cet article est de proposer l'analyse multirésolution en ondelettes en tant qu'outil efficace permettant d'améliorer la sensibilité des indicateurs scalaires (kurtosis et facteur de crête) pour l'identification des défauts mécaniques induisant des forces impulsives. En effet, ces indicateurs sont très sensibles aux variations dans le signal temporel dues aux chocs périodiques causés par le défaut. Néanmoins, leur fiabilité est immédiatement limitée en présence de niveaux intenses de bruit aléatoire associésà de faibles gravités du défaut. L'analyse Multirésolution en Ondelettes (AMRO) est proposée comme solutionà ce problème. Adaptée pour un tel objectif, plusieurs de ses paramètres d'analyse sont choisis, voire optimisés. Initialement la méthode proposée est appliquée sur un signal simulé. Pour la validation expérimentale, plusieurs séries d'expériences ontété réalisées sur des roulementsà billes età rouleaux cylindriques, sur lesquels différents défauts ontété provoqués. Les mesures ontété prises dans différentes configurations, 210 signaux ontété mesurés dans plusieurs fréquences d'échantillonnage et vitesses de rotation sur un banc d'essais, l'application industrielle est faite sur un groupe turbo-alternateur. Mots clés : Signaux de choc / analyse multirésolution en ondelettes / kurtosis / facteur de crête / détection des défauts Abstract-Optimization of wavelet multiresolution analysis of shock signals. Application to the signals generated by defective rolling bearings. The aim of this paper is to propose the wavelet analysis as an effective tool allowing to improve the sensitivity of scalar indicators (Kurtosis and crest factor) for the identification of mechanical faults inducing impulsive forces. Indeed, these indicators are very sensitive to the variations in temporal signal due to the periodic shocks caused by the defect. Nevertheless, their reliability is immediately limited by the presence of high level of random noise associated to a small gravity of the defect. Wavelet Multiresolution Analysis (WMRA) is proposed as a solution to this problem. Adapted for such objective, several of its parameters were chosen, even optimized. Initially, the proposed method is applied to simulated signal. For the experimental validation, several series of experiments were realized on ball and cylindrical roller bearings, on which various defects were caused. Measurements were taken with various configurations, 210 signals were measured at different sampling rates and rotation speeds on a laboratory test rig, the industrial application is carried out on a turbo alternator.

Research paper thumbnail of Early Detection of Mechanical Defects by Neural Networks “Spectral Analysis”

Springer eBooks, 2013

Various methods are implemented to identify the nature of a defect on a rotating machine, by usin... more Various methods are implemented to identify the nature of a defect on a rotating machine, by using vibratory measures; they differ in their precision, simplicity of implementation and their sensitivity to errors measurement. The identification of several defects combination is still difficult to implement by conventional signal processing, as the vibration signal that emerges is disturbed, thus making any identification so hard.

Research paper thumbnail of Detecting mechanical failures inducing periodical shocks by wavelet multiresolution analysis. Application to rolling bearings faults diagnosis

Research paper thumbnail of Experimental study of real gear transmission defects using sound perception

The International Journal of Advanced Manufacturing Technology, Sep 9, 2014

Research paper thumbnail of Etude du champ acoustique de plaques par intensimétrie : contribution à la définition d'une méthodologie de mesure de la puissance acoustique

La pratique de l’intensimetrie vectorielle pose aux utilisateurs differents types de probleme don... more La pratique de l’intensimetrie vectorielle pose aux utilisateurs differents types de probleme dont les plus importants sont : - la calibration des sondes , - l’influence de champ reactif sur la mesure de L'intensite active, - le choix et la discretisation de la surface de controle pour des mesures de puissance acoustique. L' etude est consacree essentiellement a ce dernier probleme et particulierement a l ' estimation des erreurs faites sur L'energie vibratoire, sur L' intensite active locale et sur la puissance acoustique. A un degre moindre , on procede a l' examen des erreurs d ' appareillage. De telles etudes ont ete menees jusqu' a present sur des emetteurs de forme simple (monopole le - dipole) et nous avons voulu examiner Le comportement vibra-acoustique d'une structure plus proche de la realite : plaque couplee a un milieu fluide (air) soumise a des excitations mecaniques ponctuelles et aeriennes (ondes planes). Une etude theorique et numerique a ete realisee en vue de stimuler la mesure de L' intensite active en tout point et de l’energie vibratoire. L' etude experimentale confirme Les tendances pour la plaque et suggere une methodologie pratique pour des structures plus complexes egalement testees (plaque e n L et boite). Son proposes : - des criteres de maillage lies a la Longueur d'onde de fl ex ion pour des structures simples. - une methode fondee sur une analyse statistique, avec des indicateurs fournissant une estimation de L' erreur commise sur La puissance acoustique de structures de forme complexe. Ce travail doit contribue r a une meilleure connaissance des phenomenes de rayonnement deceles par un intensimetre et peut constituer une base de discussion en vue de La normalisation de La mesure de puissance acoustique par intensimetrie.

Research paper thumbnail of Auditory Evaluation of Sounds Radiated from a Vibrating Plate Inside a Damped Cavity

HAL (Le Centre pour la Communication Scientifique Directe), 2009

The present investigation deals with the optimization of the vibroacoustic computational effort t... more The present investigation deals with the optimization of the vibroacoustic computational effort towards perceptual constraints. This is carried out considering the academic case of a vibrating plate coupled with a damped cavity. The study looks into a particularly restrictive parameter inherent in the computation in frequency of prediction tools: the maximum limit frequency. This parameter is aimed at being adjusted to an optimal value which allows the qualitative trends concerning the optimal structural design of the system to be kept. These qualitative trends are originally obtained from the auditory evaluation of real sounds. The real sounds correspond to the noise radiated from the plate inside the cavity, recorded in different structural configurations of the system. These configurations involve the controlled variation of three structural parameters: the cavity sound absorption properties, the plate thickness and tightening conditions. The real sounds are first pairwise submitted to listeners who are asked to give dissimilarity and preference judgments. The reference qualitative trends are then established, in terms of perceptual space, preference space and preference ranking. Afterwards, the adjustment process consists in finding out, from a low-pass filtering applied to the recorded sounds, an optimal cutoff frequency which allows the reference qualitative trends to be preserved.

Research paper thumbnail of The Influence of the Sound Pressure Level on the Identification of the Defects Severity in Gear Transmission by the Sound Perception

Acoustics Australia, Aug 8, 2019

All industrial equipment in operation generates vibrations and noise and we perceive and interpre... more All industrial equipment in operation generates vibrations and noise and we perceive and interpret them. Noise is therefore associated psychologically with the objects that emit them. The techniques of vibratory signal processing and generated sounds have allowed refining their perceptive impact and relating it to the structures characteristics. Our work essentially consists in establishing a relationship, or even a correlation, between the perceived sounds and the resulting vibrations. For this, we have studied the influence of the sound pressure level on the ability of auditors to identify the evolution of the defect severity. Two perceptual tests were performed: The first is carried out on sounds obtained directly by the conversion of vibratory signals measured on the machine. Conversely, the second test is conducted on the same sounds by equalizing their sound pressure levels, where the idea is to let the listeners focus on the content of the sounds but not on their pressure levels. The obtained results allowed the establishment of correlations between the objective and subjective aspects and to highlight the important relationships that exist between the vibratory indicators and the distances between the sounds in the proximity space. The obtained correlation coefficient from the second test, which is higher than that of the first one, shows that the equalization procedure of the sound pressure levels has a much more indicative impact on the identification of the evolution of the defects severity.

Research paper thumbnail of Perceptual study of the evolution of gear defects

Applied Acoustics, Dec 1, 2015

Abstract The objective of this work is to apply the sound perception approach to study and diagno... more Abstract The objective of this work is to apply the sound perception approach to study and diagnose gear defects. Simple and multiple defects of different levels of severity are artificially simulated on the gear teeth. The corresponding sounds are then acquired to perform a sound base representative of the diversity of gear defects. Acoustic sounds are generated using the processing software DynamX V.7. These sounds are analyzed with the paired comparison method to find a correlation between the sound perception and the scalar indicators. The results show that perception tests allow classifying gear defect sounds by order of degradation. The relation between the vibratory indicators and sound perception enabled us to obtain applicable mathematical models for the other sounds not included in the listening tests. These models can be used to monitor the evolution of gear degradation without repeating perceptions tests.

Research paper thumbnail of Optimization of wavelet multiresolution analysis of shock signals. Application to the signals generated by defective rolling bearings

HAL (Le Centre pour la Communication Scientifique Directe), 2006

ABSTRACT Cited By (since 1996):3, Export Date: 1 December 2013, Source: Scopus

Research paper thumbnail of Study of Noise Inside a Mechanical Shovel Cabin Using a Sound Perception Approach

Lecture notes in mechanical engineering, Sep 1, 2016

The use of perceptive and sound quality approaches in the mechanical field, in which it is necess... more The use of perceptive and sound quality approaches in the mechanical field, in which it is necessary to establish the link between the conception (taking an interest in the object producing noise) of the mechanical system and the auditory perception (taking an interest in the noise emitted), is still considered as rather new. Perceptive analysis allows extracting information making it possible to use well-adapted physical analysis methods and metrics so as to better choose the technical responses to a noise problem [1, 2]. In the case of a mechanical shovel (Volvo Compact), perceptive tests of comparisons by pairs have been used to define only the necessary frequency bands of the noise studied and classifying their participation as a function of subjective (annoyance, etc.) and objective (global level) terms [3]. The utility of modeling adapted to low frequencies (BEM or FEM) has been shown when simulating structural modifications and assessing their effects on the interior noise of a mechanical shovel cabin. Manufacturers need a predictive model of sound annoyance for a complete machine and identify those of its elements which contribute to annoyance, so as to implement a hierarchical noise reduction approach inside the cabin. A prediction model of sound preference that can be used to identify the procedure for improving sound annoyance from simulations has been built and validated [4].

Research paper thumbnail of Subjective evaluations of sound radiated by impacted plates, using the design of experiments method

Applied Acoustics, Jun 1, 2010

This study combines physical and subjective approaches to evaluate the sound quality of impacted ... more This study combines physical and subjective approaches to evaluate the sound quality of impacted plates. A numerical model, based on the Hertz law of contact, has been used to determine the sound pressure level at any point in space resulting from an impact. Sounds synthesized using this model and those from experiments can then be exploited in a physical analysis and/or a subjective analysis of the effects associated with variations in parameters. Here the influence of certain physical parameters on the sound perception of impacted plates is evaluated through a design of experiments method and a subjective test of preference. The subjective test is based on an estimate of preference between two pairs of synthetic sounds by varying several structural parameters at the same time. This differs from other studies that vary only one parameter at a time and fix the other parameters.

Research paper thumbnail of Experimental Study of Real Gear Transmission Defects Using Sound Perception

Lecture notes in mechanical engineering, Sep 1, 2016

Research paper thumbnail of Localisation de l'excitation à partir de la déformée d'une poutre en utilisant les réseaux de neurones

HAL (Le Centre pour la Communication Scientifique Directe), Mar 23, 2005

Research paper thumbnail of Détection des défauts mécaniques par réseaux de neurones, Analyse sur banc d'essai expérimental

HAL (Le Centre pour la Communication Scientifique Directe), 2008

Research paper thumbnail of Detection mechanical defects by neural networks. Experimental analysis

HAL (Le Centre pour la Communication Scientifique Directe), 2012

Research paper thumbnail of Evaluation des indicateurs de surveillance par analyse vibratoire : Application aux engrenages et roulements

In this paper, we evaluate several criteria of vibration analysis signal in the temporal field. T... more In this paper, we evaluate several criteria of vibration analysis signal in the temporal field. The objective is to evaluate their ability to detect a single or multiple fault, their ability to evaluate the severity of a bearing fault, and their ability to detect sound gearing or faulty gearing in different fault configurations created on the gear and bearing mounted on an experimental test stand. In order to evaluate the robustness of each criterion, operating parameters of the machines are taking into account in the experimental design to carry out tests under various conditions of use of the machine. We take into account parameters such as speed and load that we experiment different values to determine their influences on the criteria studied. If we identify the criterion under these conditions, then it is very likely that this is the appropriate criterion to detect the type of defect involved.

Research paper thumbnail of Detection of rolling bearing defects using discrete wavelet analysis

Meccanica, Nov 29, 2007

In the detection of bearing faults the so much desired objective remains the extraction of the de... more In the detection of bearing faults the so much desired objective remains the extraction of the defect vibratory signature from the measured signal in which immerses the random noise and other components of the machine. In this article a denoising method of the measured signals is presented. Based on the optimization of wavelet multiresolution analysis, it uses the kurtosis as an optimization and evaluation criterion, several parameters were then selected. The experimental results show the validity of this method within the detection of several defects simulated on ball bearings. The various configurations, in which the signals were measured, allow leading to optimum conditions of its application. The application of WMRA on filtered signals allows better results than its application on wide bands signals or a simple band pass filtering.

Research paper thumbnail of Comparative study between objective and subjective methods for identifying the gravity of single and multiple gear defects in case of noisy signals

Applied Acoustics, 2022

Abstract This paper aims to compare two approaches for the identification of gear defects in a ve... more Abstract This paper aims to compare two approaches for the identification of gear defects in a very noisy environment. The first one, called subjective, is based on sound perception using paired comparison test; the second, objective, is based on vibration analysis using three advanced signal processing methods. The first part of the paper determines a correlation between the sound perception obtained by the listeners and the scalar indicators calculated for different gravities of gear defects (simple and/or double). The perception test was carried out on sounds obtained directly by converting the measured vibratory signals. The study is conducted in a two-dimensional proximity space. The results obtained allowed the determination of mathematical models that correlate between the objective and subjective aspects and highlight the important relationship between the vibratory indicators and the distances between the sounds in the perceptual space. The correlation ratios obtained for the first dimension (DIM1) prove to be very significant. In the second part of the paper, the same signals are processed by three methods, known to be powerful tools in vibratory signal processing, namely Optimized Wavelet Multi-Resolution Analysis (WMRA), cyclostationary analysis, and a hybrid approach based on an improved version of the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) and multivariate denoising by wavelets and PCA (Principal Component Analysis). For all three methods considered, a demodulation approach is performed to obtain an envelope spectrum as a final result. In the case of very noisy signals, the subjective method allows a better assessment of the evolution of the severity of the gear defects compared to the objective methods used. In our opinion, this is due to the high sensitivity of the human ear to identify the existence of a defect and to assess its degree of severity, far better than the most sophisticated objective signal processing methods, which remain limited in the case of very noisy signals.

Research paper thumbnail of Optimisation de l'analyse statistique des signaux vibratoires induits par des roulements défectueux

HAL (Le Centre pour la Communication Scientifique Directe), 2007

Research paper thumbnail of Perceptual Study of Simple and Combined Gear Defects

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2017

Research paper thumbnail of Optimisation de l'analyse multirésolution en ondelettes pour la détection précoce des défauts de roulements

HAL (Le Centre pour la Communication Scientifique Directe), 2006

-L'objectif de cet article est de proposer l'analyse multirésolution en ondelettes en tant qu'out... more -L'objectif de cet article est de proposer l'analyse multirésolution en ondelettes en tant qu'outil efficace permettant d'améliorer la sensibilité des indicateurs scalaires (kurtosis et facteur de crête) pour l'identification des défauts mécaniques induisant des forces impulsives. En effet, ces indicateurs sont très sensibles aux variations dans le signal temporel dues aux chocs périodiques causés par le défaut. Néanmoins, leur fiabilité est immédiatement limitée en présence de niveaux intenses de bruit aléatoire associésà de faibles gravités du défaut. L'analyse Multirésolution en Ondelettes (AMRO) est proposée comme solutionà ce problème. Adaptée pour un tel objectif, plusieurs de ses paramètres d'analyse sont choisis, voire optimisés. Initialement la méthode proposée est appliquée sur un signal simulé. Pour la validation expérimentale, plusieurs séries d'expériences ontété réalisées sur des roulementsà billes età rouleaux cylindriques, sur lesquels différents défauts ontété provoqués. Les mesures ontété prises dans différentes configurations, 210 signaux ontété mesurés dans plusieurs fréquences d'échantillonnage et vitesses de rotation sur un banc d'essais, l'application industrielle est faite sur un groupe turbo-alternateur. Mots clés : Signaux de choc / analyse multirésolution en ondelettes / kurtosis / facteur de crête / détection des défauts Abstract-Optimization of wavelet multiresolution analysis of shock signals. Application to the signals generated by defective rolling bearings. The aim of this paper is to propose the wavelet analysis as an effective tool allowing to improve the sensitivity of scalar indicators (Kurtosis and crest factor) for the identification of mechanical faults inducing impulsive forces. Indeed, these indicators are very sensitive to the variations in temporal signal due to the periodic shocks caused by the defect. Nevertheless, their reliability is immediately limited by the presence of high level of random noise associated to a small gravity of the defect. Wavelet Multiresolution Analysis (WMRA) is proposed as a solution to this problem. Adapted for such objective, several of its parameters were chosen, even optimized. Initially, the proposed method is applied to simulated signal. For the experimental validation, several series of experiments were realized on ball and cylindrical roller bearings, on which various defects were caused. Measurements were taken with various configurations, 210 signals were measured at different sampling rates and rotation speeds on a laboratory test rig, the industrial application is carried out on a turbo alternator.

Research paper thumbnail of Early Detection of Mechanical Defects by Neural Networks “Spectral Analysis”

Springer eBooks, 2013

Various methods are implemented to identify the nature of a defect on a rotating machine, by usin... more Various methods are implemented to identify the nature of a defect on a rotating machine, by using vibratory measures; they differ in their precision, simplicity of implementation and their sensitivity to errors measurement. The identification of several defects combination is still difficult to implement by conventional signal processing, as the vibration signal that emerges is disturbed, thus making any identification so hard.

Research paper thumbnail of Detecting mechanical failures inducing periodical shocks by wavelet multiresolution analysis. Application to rolling bearings faults diagnosis

Research paper thumbnail of Experimental study of real gear transmission defects using sound perception

The International Journal of Advanced Manufacturing Technology, Sep 9, 2014

Research paper thumbnail of Etude du champ acoustique de plaques par intensimétrie : contribution à la définition d'une méthodologie de mesure de la puissance acoustique

La pratique de l’intensimetrie vectorielle pose aux utilisateurs differents types de probleme don... more La pratique de l’intensimetrie vectorielle pose aux utilisateurs differents types de probleme dont les plus importants sont : - la calibration des sondes , - l’influence de champ reactif sur la mesure de L'intensite active, - le choix et la discretisation de la surface de controle pour des mesures de puissance acoustique. L' etude est consacree essentiellement a ce dernier probleme et particulierement a l ' estimation des erreurs faites sur L'energie vibratoire, sur L' intensite active locale et sur la puissance acoustique. A un degre moindre , on procede a l' examen des erreurs d ' appareillage. De telles etudes ont ete menees jusqu' a present sur des emetteurs de forme simple (monopole le - dipole) et nous avons voulu examiner Le comportement vibra-acoustique d'une structure plus proche de la realite : plaque couplee a un milieu fluide (air) soumise a des excitations mecaniques ponctuelles et aeriennes (ondes planes). Une etude theorique et numerique a ete realisee en vue de stimuler la mesure de L' intensite active en tout point et de l’energie vibratoire. L' etude experimentale confirme Les tendances pour la plaque et suggere une methodologie pratique pour des structures plus complexes egalement testees (plaque e n L et boite). Son proposes : - des criteres de maillage lies a la Longueur d'onde de fl ex ion pour des structures simples. - une methode fondee sur une analyse statistique, avec des indicateurs fournissant une estimation de L' erreur commise sur La puissance acoustique de structures de forme complexe. Ce travail doit contribue r a une meilleure connaissance des phenomenes de rayonnement deceles par un intensimetre et peut constituer une base de discussion en vue de La normalisation de La mesure de puissance acoustique par intensimetrie.

Research paper thumbnail of Auditory Evaluation of Sounds Radiated from a Vibrating Plate Inside a Damped Cavity

HAL (Le Centre pour la Communication Scientifique Directe), 2009

The present investigation deals with the optimization of the vibroacoustic computational effort t... more The present investigation deals with the optimization of the vibroacoustic computational effort towards perceptual constraints. This is carried out considering the academic case of a vibrating plate coupled with a damped cavity. The study looks into a particularly restrictive parameter inherent in the computation in frequency of prediction tools: the maximum limit frequency. This parameter is aimed at being adjusted to an optimal value which allows the qualitative trends concerning the optimal structural design of the system to be kept. These qualitative trends are originally obtained from the auditory evaluation of real sounds. The real sounds correspond to the noise radiated from the plate inside the cavity, recorded in different structural configurations of the system. These configurations involve the controlled variation of three structural parameters: the cavity sound absorption properties, the plate thickness and tightening conditions. The real sounds are first pairwise submitted to listeners who are asked to give dissimilarity and preference judgments. The reference qualitative trends are then established, in terms of perceptual space, preference space and preference ranking. Afterwards, the adjustment process consists in finding out, from a low-pass filtering applied to the recorded sounds, an optimal cutoff frequency which allows the reference qualitative trends to be preserved.

Research paper thumbnail of The Influence of the Sound Pressure Level on the Identification of the Defects Severity in Gear Transmission by the Sound Perception

Acoustics Australia, Aug 8, 2019

All industrial equipment in operation generates vibrations and noise and we perceive and interpre... more All industrial equipment in operation generates vibrations and noise and we perceive and interpret them. Noise is therefore associated psychologically with the objects that emit them. The techniques of vibratory signal processing and generated sounds have allowed refining their perceptive impact and relating it to the structures characteristics. Our work essentially consists in establishing a relationship, or even a correlation, between the perceived sounds and the resulting vibrations. For this, we have studied the influence of the sound pressure level on the ability of auditors to identify the evolution of the defect severity. Two perceptual tests were performed: The first is carried out on sounds obtained directly by the conversion of vibratory signals measured on the machine. Conversely, the second test is conducted on the same sounds by equalizing their sound pressure levels, where the idea is to let the listeners focus on the content of the sounds but not on their pressure levels. The obtained results allowed the establishment of correlations between the objective and subjective aspects and to highlight the important relationships that exist between the vibratory indicators and the distances between the sounds in the proximity space. The obtained correlation coefficient from the second test, which is higher than that of the first one, shows that the equalization procedure of the sound pressure levels has a much more indicative impact on the identification of the evolution of the defects severity.

Research paper thumbnail of Perceptual study of the evolution of gear defects

Applied Acoustics, Dec 1, 2015

Abstract The objective of this work is to apply the sound perception approach to study and diagno... more Abstract The objective of this work is to apply the sound perception approach to study and diagnose gear defects. Simple and multiple defects of different levels of severity are artificially simulated on the gear teeth. The corresponding sounds are then acquired to perform a sound base representative of the diversity of gear defects. Acoustic sounds are generated using the processing software DynamX V.7. These sounds are analyzed with the paired comparison method to find a correlation between the sound perception and the scalar indicators. The results show that perception tests allow classifying gear defect sounds by order of degradation. The relation between the vibratory indicators and sound perception enabled us to obtain applicable mathematical models for the other sounds not included in the listening tests. These models can be used to monitor the evolution of gear degradation without repeating perceptions tests.

Research paper thumbnail of Optimization of wavelet multiresolution analysis of shock signals. Application to the signals generated by defective rolling bearings

HAL (Le Centre pour la Communication Scientifique Directe), 2006

ABSTRACT Cited By (since 1996):3, Export Date: 1 December 2013, Source: Scopus

Research paper thumbnail of Study of Noise Inside a Mechanical Shovel Cabin Using a Sound Perception Approach

Lecture notes in mechanical engineering, Sep 1, 2016

The use of perceptive and sound quality approaches in the mechanical field, in which it is necess... more The use of perceptive and sound quality approaches in the mechanical field, in which it is necessary to establish the link between the conception (taking an interest in the object producing noise) of the mechanical system and the auditory perception (taking an interest in the noise emitted), is still considered as rather new. Perceptive analysis allows extracting information making it possible to use well-adapted physical analysis methods and metrics so as to better choose the technical responses to a noise problem [1, 2]. In the case of a mechanical shovel (Volvo Compact), perceptive tests of comparisons by pairs have been used to define only the necessary frequency bands of the noise studied and classifying their participation as a function of subjective (annoyance, etc.) and objective (global level) terms [3]. The utility of modeling adapted to low frequencies (BEM or FEM) has been shown when simulating structural modifications and assessing their effects on the interior noise of a mechanical shovel cabin. Manufacturers need a predictive model of sound annoyance for a complete machine and identify those of its elements which contribute to annoyance, so as to implement a hierarchical noise reduction approach inside the cabin. A prediction model of sound preference that can be used to identify the procedure for improving sound annoyance from simulations has been built and validated [4].

Research paper thumbnail of Subjective evaluations of sound radiated by impacted plates, using the design of experiments method

Applied Acoustics, Jun 1, 2010

This study combines physical and subjective approaches to evaluate the sound quality of impacted ... more This study combines physical and subjective approaches to evaluate the sound quality of impacted plates. A numerical model, based on the Hertz law of contact, has been used to determine the sound pressure level at any point in space resulting from an impact. Sounds synthesized using this model and those from experiments can then be exploited in a physical analysis and/or a subjective analysis of the effects associated with variations in parameters. Here the influence of certain physical parameters on the sound perception of impacted plates is evaluated through a design of experiments method and a subjective test of preference. The subjective test is based on an estimate of preference between two pairs of synthetic sounds by varying several structural parameters at the same time. This differs from other studies that vary only one parameter at a time and fix the other parameters.