Xavier Cristol - Academia.edu (original) (raw)
Papers by Xavier Cristol
... 8 2.2 Lambert-Mackenzie 9 2.3 Lambert's rule with threshold at low grazing angles 10... more ... 8 2.2 Lambert-Mackenzie 9 2.3 Lambert's rule with threshold at low grazing angles 10 ... The model is frequency independent. The value of the coefficient depends on the bottom type. Mackenzie [2] found that a value of 10 log10 = -27 dB fitted his data (530 and 1030 Hz) well. ...
OCEANS 2019 - Marseille
Recent advances and evolutions of the ALMA (Acoustic Laboratory for Marine Applications) project ... more Recent advances and evolutions of the ALMA (Acoustic Laboratory for Marine Applications) project are tackled in this paper. While the system’s goal continues to gather experimental data to share with the community and understand the underlying phenomena linked with ocean fluctuations and their interactions with sound waves propagation, the technological and technical updates of the system also allowed to conduct some measurements of the ambient noise properties. Both of these two aspects of the work conducted with ALMA are the topic of this paper: on one hand, the effect of temperature fluctuations on the variation of the estimated direction of arrival of acoustic waves emitted from a fixed source was previously shown and is studied here from a statistical point of view. In fact, the distribution of the normalized acoustic intensity is computed in different configurations and serves as an efficient tool to discriminate between the various regimes of fluctuations involved. On the other hand, noise properties (directivity, coherence) are studied and the design of the 2018 ALMA passive acoustic array is discussed.
OCEANS 2018 MTS/IEEE Charleston, 2018
This paper presents an active sonar localization method from a passive array. The main difficulty... more This paper presents an active sonar localization method from a passive array. The main difficulty in the passive exploitation of the sonar pulse received and detected by an array is that the transmitted waveform is unknown. This difficulty may be overcome by considering as reference waveform the signal in the beam with maximal energy. We then compute the cross-correlation between the reference signal and the signals in all other beams and we get a constellation of angle-delay points corresponding to the multiple paths in the channel connecting the source to the receiver. We finally estimate the target position by minimizing the Hausdorff Distance between the observed angle-delay pairs and simulated pairs for a sampling of the source possible positions. This localization method has been tested on the real data collected during the ALMA 2015 campaing (shallow-water configuration) and on simulated data in several deep-water configurations.
Les auteurs s'interessent ici a l'etude d'une experimentation a echelle reduite. L... more Les auteurs s'interessent ici a l'etude d'une experimentation a echelle reduite. L'objectif in fine est de reproduire les effets de fluctuations du milieu sur la propagation des ondes acoustiques en milieu marin. Pour cela, l'adaptation du calcul des parametres adimensionnels utilises en general pour definir les regimes de fluctuations est proposee. Le but du present article est de presenter les calculs menant a l'evaluation de ces parametres adimensionnels. Le procede repose sur le calcul analytique du champ acoustique propage au travers d'une lentille acoustique presentant une face d'entree plane et une face de sortie aleatoirement rugueuse. Des statistiques sur le champ acous-tique (moments du premier et du second ordre) et les noyaux de sensibilite ont permis l'evaluation des parametres strength et diffraction, ainsi que du rapport entre la longueur de correlation du champ acoustique et la longueur d'onde. Une continuite entre notre protoc...
Abstract: This paper addresses the problem of source localization with only one sensor. A new met... more Abstract: This paper addresses the problem of source localization with only one sensor. A new metric called Hausdorff Distance (HD) for an optimal matching, is used for TDOAs best matching between simulations (TDOAs) and real data (TDOAr). To obtain the simulated impulse response, we drive an acoustic ray path propagation method. So we compare these simulated data with TDOA estimated after matched filtering considering a known transmitted signal. Two derivated techniques from HD are presented to find correct position, in range and depth, 1) the Maximum Hausdorff distance and 2) the Median Hausdorff distance. Results in terms of the localization, accuracy are shown in a real tank experiment.
We reproduce, using scaled experiments in a water tank, the effects of scattering phenomena respo... more We reproduce, using scaled experiments in a water tank, the effects of scattering phenomena responsible for the degradations of sonar system performances in oceanic environment (typically, the small sound speed fluctuations associated with linear internal waves). We reproduce a wide panel of scattering effects, spanning from " simple " phase aberrations up to radical changes in the sound field structure (appearance of caustics). An experimental protocol was developed. It consists in transmitting a high-frequency wave train (ultrasonic pressure field around 2MHz) through wax lenses with randomly rough faces, that induce distortions comparable to those that would be observed at sea at around 1kHz in the case of a lower frequency acoustic signal travelling through a linear internal wave field. Using a 3-D printer, we were able to manufacture lenses with a randomly rough face characterized by its amplitude and vertical and horizontal correlation lengths. The dependence of the ...
Global Oceans 2020: Singapore – U.S. Gulf Coast, 2020
This paper presents a method to localize with a passive array an acoustic source emitting high So... more This paper presents a method to localize with a passive array an acoustic source emitting high Sound-to-Noise Ratio (SNR) Continuous Waves (CW). The method consists in measuring the elevation angle of the multiple paths between the source and the receiver and to estimate the source location by comparing, with the Hausdorff distance, the measured elevation angles with angles simulated for a sampling of the source possible positions. The procedure is tested on the real acoustic signals collected by DGA Naval Systems during the experimental deepwater 2018 ALMA campaign. During this campaign, both the source and the passive array were hung below a boat so that the orientation of the array was uncertain and varying with time. The localization technique had then to be modified to take into account the movement of the array.
Localize a real signal in a tank in range and in depth, in order to define the best approach for ... more Localize a real signal in a tank in range and in depth, in order to define the best approach for localization problem. • Test two techiniques, Hausdroff Distance, and Sum of minimum distance), to compare the TDOA recorded in the tank and simulated in Matlab using a ray propagation code, in order to find the minimum error that correspond the correct position.
The Journal of the Acoustical Society of America, 2021
This paper examines the scattering of a monochromatic acoustic wave by sea-surface gravity waves ... more This paper examines the scattering of a monochromatic acoustic wave by sea-surface gravity waves in the 1-200 Hz frequency range. The source is moving in a straight line at a constant speed, and the acoustic waves are traveling upward in a refractive channel. Considering the scales of the problem, the small perturbation method coupled with the normal-mode theory and an asymptotic analysis are used to derive the first-order scattered pressure field p1. This method, established by Labianca and Harper [J. Acoust. Soc. Am. 61(2), 378-389 (1977)], allows p1 to be expressed with normal-mode functions, which are computed numerically using the in-house modal propagation code MOCTESUMA for any sound-speed profile. The pressure field is calculated in a deep-water configuration with a moving source inside a summer thermocline. First, the spatial distribution of p1 is found to follow the diffraction grating formula. Particular attention is drawn to the border between the propagative and evanesc...
The Journal of the Acoustical Society of America, 2021
The Journal of the Acoustical Society of America, 2011
... Abrahamsson L, Andersson BL, Ivansson S, Pihl J, Ainslie M, Benders F, Colin M, van Vossen R,... more ... Abrahamsson L, Andersson BL, Ivansson S, Pihl J, Ainslie M, Benders F, Colin M, van Vossen R, Chalindar B, Cristol X, Juhel B ... The bottom parameters are the Lambert back-scattering parameter and the sound speed c, density ρ, absorption α, and thickness of the sediment. ...
The European Defence Agency project RUMBLE-2 (ref.[1]) offered the opportunity for investigating ... more The European Defence Agency project RUMBLE-2 (ref.[1]) offered the opportunity for investigating experimentally acoustic reverberation at about 1.kHz, under grazing incidence (less than about 20°), from very porous clayey seafloors of a continental shelf (mean grain size spanning from about 7 to 10 in units); the instrument was an operational, carefully calibrated LF towed triplet-array sonar. Assuming Lambert law, observed values for the normal backscattering strength μ0 spanned between –20 dB to –12 dB, i.e. 10-15 dB higher than usually recommended values for soft seabeds. The objective of this article is to understand such high values of inverted μ0’s during the RUMBLE2 experiments, which appear at first glance considerably high, particularly when considering the nature of the sedimentary cover. As displayed by the map on the left of Figure 1, the inverted μ0’s are ranging from about –20 to –12 dB, for a seabed covered by very thin clays with Mean Grain Sizes of 8 to 10 units (porosities more than 85%), as shown by the chart on the right of Figure 1. Usually recommended values for μ0 are 10 to 15 dB lower, or even more; we have to explain such a disturbing discrepancy.
OCEANS 2017 - Aberdeen, 2017
This paper addresses the problem of localizing and tracking a surface or underwater vessel with t... more This paper addresses the problem of localizing and tracking a surface or underwater vessel with the technique called as Hausdorff Distance. Two proposed approaches, based on TDOAs comparison, were used for 2-D localization, in range and depth, with one sensor only, and have been successfully applied to localize a motionless unknown target in a tank's experiment. Results in terms of the localization accuracy have been obtained with real signal and the performance of the proposed localization techniques have been demonstrated and confirmed by simulation with respect of signal-to-noise ratio and compared with the correlation techniques used nowadays for single hydrophones.
2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO), 2018
The fundamental and practical problem of passive localization in range and depth, of an acoustic ... more The fundamental and practical problem of passive localization in range and depth, of an acoustic underwater source is addressed, with application to an at-sea experiment. We propose and try a new matching method based on a metric called as Hausdorff distance as a cost-function to be minimized, in order to perform the localization inversion. The data set analyzed here was collected during the DGA campaign ALMA 2015, which took place in a shallow water environment of the southern coast of France. Acoustic data were measured over a 10m-high vertical linear array (VLA), composed of 64 hydrophones. The 2-D localization, in range and depth, is performed by matching the patterns of time difference of arrival (TDOA), between respectively observed and modeled sequences. Several variants of the Hausdorff Distance are applied, firstly separately in each single hydrophone, and then combined in order to improve the localization accuracy, reducing the ambiguity either is depth and in range. The performance is evaluated in terms of the localization accuracy of the proposed method, in a context of passive localization with a cooperative system considering a motionless target. Very satisfactory performance and accuracy are obtained.
Acta Acustica united with Acustica, 2017
A scaled experimental protocol, in a water tank, is proposed to mimic the effects of medium heter... more A scaled experimental protocol, in a water tank, is proposed to mimic the effects of medium heterogeneities on underwater acoustic propagation. The procedure consists in transmitting an ultrasonic wave (f = 2.25 MHz) through a RAndom Faced Acoustic Lens (RAFAL) in order to induce a spatially fluctuating sound pressure field. A scaling process based on a dimensional analysis ensures the representativeness of the experiment, when compared to the fluctuations of a few kHz continuous waves in the ocean. The regimes of saturation and unsaturation are explored by tuning the statistical parameters of the RAFAL's output face, the signal frequency and the propagation distance in the water tank. The control and reproducibility of the measurements is therefore ensured. The influence of volume effects is especially studied, since the experiments were conducted in free field conditions. Results in terms of mutual coherence function (second-order moment) are presented ; a good agreement is found between the values of radii of coherence calculated using experimental and simulation data, as well as theoretical results. The evaluation of the complex pressure distribution highlights the relevance of the experimental scheme, since behaviors typical of the regimes of fluctuations (saturation and unsaturation) are found.
The Journal of the Acoustical Society of America
Articles you may be interested in Stochastic matched-field localization of an acoustic source bas... more Articles you may be interested in Stochastic matched-field localization of an acoustic source based on principles of Riemannian geometry
IEEE Journal of Selected Topics in Signal Processing
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
... 8 2.2 Lambert-Mackenzie 9 2.3 Lambert's rule with threshold at low grazing angles 10... more ... 8 2.2 Lambert-Mackenzie 9 2.3 Lambert's rule with threshold at low grazing angles 10 ... The model is frequency independent. The value of the coefficient depends on the bottom type. Mackenzie [2] found that a value of 10 log10 = -27 dB fitted his data (530 and 1030 Hz) well. ...
OCEANS 2019 - Marseille
Recent advances and evolutions of the ALMA (Acoustic Laboratory for Marine Applications) project ... more Recent advances and evolutions of the ALMA (Acoustic Laboratory for Marine Applications) project are tackled in this paper. While the system’s goal continues to gather experimental data to share with the community and understand the underlying phenomena linked with ocean fluctuations and their interactions with sound waves propagation, the technological and technical updates of the system also allowed to conduct some measurements of the ambient noise properties. Both of these two aspects of the work conducted with ALMA are the topic of this paper: on one hand, the effect of temperature fluctuations on the variation of the estimated direction of arrival of acoustic waves emitted from a fixed source was previously shown and is studied here from a statistical point of view. In fact, the distribution of the normalized acoustic intensity is computed in different configurations and serves as an efficient tool to discriminate between the various regimes of fluctuations involved. On the other hand, noise properties (directivity, coherence) are studied and the design of the 2018 ALMA passive acoustic array is discussed.
OCEANS 2018 MTS/IEEE Charleston, 2018
This paper presents an active sonar localization method from a passive array. The main difficulty... more This paper presents an active sonar localization method from a passive array. The main difficulty in the passive exploitation of the sonar pulse received and detected by an array is that the transmitted waveform is unknown. This difficulty may be overcome by considering as reference waveform the signal in the beam with maximal energy. We then compute the cross-correlation between the reference signal and the signals in all other beams and we get a constellation of angle-delay points corresponding to the multiple paths in the channel connecting the source to the receiver. We finally estimate the target position by minimizing the Hausdorff Distance between the observed angle-delay pairs and simulated pairs for a sampling of the source possible positions. This localization method has been tested on the real data collected during the ALMA 2015 campaing (shallow-water configuration) and on simulated data in several deep-water configurations.
Les auteurs s'interessent ici a l'etude d'une experimentation a echelle reduite. L... more Les auteurs s'interessent ici a l'etude d'une experimentation a echelle reduite. L'objectif in fine est de reproduire les effets de fluctuations du milieu sur la propagation des ondes acoustiques en milieu marin. Pour cela, l'adaptation du calcul des parametres adimensionnels utilises en general pour definir les regimes de fluctuations est proposee. Le but du present article est de presenter les calculs menant a l'evaluation de ces parametres adimensionnels. Le procede repose sur le calcul analytique du champ acoustique propage au travers d'une lentille acoustique presentant une face d'entree plane et une face de sortie aleatoirement rugueuse. Des statistiques sur le champ acous-tique (moments du premier et du second ordre) et les noyaux de sensibilite ont permis l'evaluation des parametres strength et diffraction, ainsi que du rapport entre la longueur de correlation du champ acoustique et la longueur d'onde. Une continuite entre notre protoc...
Abstract: This paper addresses the problem of source localization with only one sensor. A new met... more Abstract: This paper addresses the problem of source localization with only one sensor. A new metric called Hausdorff Distance (HD) for an optimal matching, is used for TDOAs best matching between simulations (TDOAs) and real data (TDOAr). To obtain the simulated impulse response, we drive an acoustic ray path propagation method. So we compare these simulated data with TDOA estimated after matched filtering considering a known transmitted signal. Two derivated techniques from HD are presented to find correct position, in range and depth, 1) the Maximum Hausdorff distance and 2) the Median Hausdorff distance. Results in terms of the localization, accuracy are shown in a real tank experiment.
We reproduce, using scaled experiments in a water tank, the effects of scattering phenomena respo... more We reproduce, using scaled experiments in a water tank, the effects of scattering phenomena responsible for the degradations of sonar system performances in oceanic environment (typically, the small sound speed fluctuations associated with linear internal waves). We reproduce a wide panel of scattering effects, spanning from " simple " phase aberrations up to radical changes in the sound field structure (appearance of caustics). An experimental protocol was developed. It consists in transmitting a high-frequency wave train (ultrasonic pressure field around 2MHz) through wax lenses with randomly rough faces, that induce distortions comparable to those that would be observed at sea at around 1kHz in the case of a lower frequency acoustic signal travelling through a linear internal wave field. Using a 3-D printer, we were able to manufacture lenses with a randomly rough face characterized by its amplitude and vertical and horizontal correlation lengths. The dependence of the ...
Global Oceans 2020: Singapore – U.S. Gulf Coast, 2020
This paper presents a method to localize with a passive array an acoustic source emitting high So... more This paper presents a method to localize with a passive array an acoustic source emitting high Sound-to-Noise Ratio (SNR) Continuous Waves (CW). The method consists in measuring the elevation angle of the multiple paths between the source and the receiver and to estimate the source location by comparing, with the Hausdorff distance, the measured elevation angles with angles simulated for a sampling of the source possible positions. The procedure is tested on the real acoustic signals collected by DGA Naval Systems during the experimental deepwater 2018 ALMA campaign. During this campaign, both the source and the passive array were hung below a boat so that the orientation of the array was uncertain and varying with time. The localization technique had then to be modified to take into account the movement of the array.
Localize a real signal in a tank in range and in depth, in order to define the best approach for ... more Localize a real signal in a tank in range and in depth, in order to define the best approach for localization problem. • Test two techiniques, Hausdroff Distance, and Sum of minimum distance), to compare the TDOA recorded in the tank and simulated in Matlab using a ray propagation code, in order to find the minimum error that correspond the correct position.
The Journal of the Acoustical Society of America, 2021
This paper examines the scattering of a monochromatic acoustic wave by sea-surface gravity waves ... more This paper examines the scattering of a monochromatic acoustic wave by sea-surface gravity waves in the 1-200 Hz frequency range. The source is moving in a straight line at a constant speed, and the acoustic waves are traveling upward in a refractive channel. Considering the scales of the problem, the small perturbation method coupled with the normal-mode theory and an asymptotic analysis are used to derive the first-order scattered pressure field p1. This method, established by Labianca and Harper [J. Acoust. Soc. Am. 61(2), 378-389 (1977)], allows p1 to be expressed with normal-mode functions, which are computed numerically using the in-house modal propagation code MOCTESUMA for any sound-speed profile. The pressure field is calculated in a deep-water configuration with a moving source inside a summer thermocline. First, the spatial distribution of p1 is found to follow the diffraction grating formula. Particular attention is drawn to the border between the propagative and evanesc...
The Journal of the Acoustical Society of America, 2021
The Journal of the Acoustical Society of America, 2011
... Abrahamsson L, Andersson BL, Ivansson S, Pihl J, Ainslie M, Benders F, Colin M, van Vossen R,... more ... Abrahamsson L, Andersson BL, Ivansson S, Pihl J, Ainslie M, Benders F, Colin M, van Vossen R, Chalindar B, Cristol X, Juhel B ... The bottom parameters are the Lambert back-scattering parameter and the sound speed c, density ρ, absorption α, and thickness of the sediment. ...
The European Defence Agency project RUMBLE-2 (ref.[1]) offered the opportunity for investigating ... more The European Defence Agency project RUMBLE-2 (ref.[1]) offered the opportunity for investigating experimentally acoustic reverberation at about 1.kHz, under grazing incidence (less than about 20°), from very porous clayey seafloors of a continental shelf (mean grain size spanning from about 7 to 10 in units); the instrument was an operational, carefully calibrated LF towed triplet-array sonar. Assuming Lambert law, observed values for the normal backscattering strength μ0 spanned between –20 dB to –12 dB, i.e. 10-15 dB higher than usually recommended values for soft seabeds. The objective of this article is to understand such high values of inverted μ0’s during the RUMBLE2 experiments, which appear at first glance considerably high, particularly when considering the nature of the sedimentary cover. As displayed by the map on the left of Figure 1, the inverted μ0’s are ranging from about –20 to –12 dB, for a seabed covered by very thin clays with Mean Grain Sizes of 8 to 10 units (porosities more than 85%), as shown by the chart on the right of Figure 1. Usually recommended values for μ0 are 10 to 15 dB lower, or even more; we have to explain such a disturbing discrepancy.
OCEANS 2017 - Aberdeen, 2017
This paper addresses the problem of localizing and tracking a surface or underwater vessel with t... more This paper addresses the problem of localizing and tracking a surface or underwater vessel with the technique called as Hausdorff Distance. Two proposed approaches, based on TDOAs comparison, were used for 2-D localization, in range and depth, with one sensor only, and have been successfully applied to localize a motionless unknown target in a tank's experiment. Results in terms of the localization accuracy have been obtained with real signal and the performance of the proposed localization techniques have been demonstrated and confirmed by simulation with respect of signal-to-noise ratio and compared with the correlation techniques used nowadays for single hydrophones.
2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO), 2018
The fundamental and practical problem of passive localization in range and depth, of an acoustic ... more The fundamental and practical problem of passive localization in range and depth, of an acoustic underwater source is addressed, with application to an at-sea experiment. We propose and try a new matching method based on a metric called as Hausdorff distance as a cost-function to be minimized, in order to perform the localization inversion. The data set analyzed here was collected during the DGA campaign ALMA 2015, which took place in a shallow water environment of the southern coast of France. Acoustic data were measured over a 10m-high vertical linear array (VLA), composed of 64 hydrophones. The 2-D localization, in range and depth, is performed by matching the patterns of time difference of arrival (TDOA), between respectively observed and modeled sequences. Several variants of the Hausdorff Distance are applied, firstly separately in each single hydrophone, and then combined in order to improve the localization accuracy, reducing the ambiguity either is depth and in range. The performance is evaluated in terms of the localization accuracy of the proposed method, in a context of passive localization with a cooperative system considering a motionless target. Very satisfactory performance and accuracy are obtained.
Acta Acustica united with Acustica, 2017
A scaled experimental protocol, in a water tank, is proposed to mimic the effects of medium heter... more A scaled experimental protocol, in a water tank, is proposed to mimic the effects of medium heterogeneities on underwater acoustic propagation. The procedure consists in transmitting an ultrasonic wave (f = 2.25 MHz) through a RAndom Faced Acoustic Lens (RAFAL) in order to induce a spatially fluctuating sound pressure field. A scaling process based on a dimensional analysis ensures the representativeness of the experiment, when compared to the fluctuations of a few kHz continuous waves in the ocean. The regimes of saturation and unsaturation are explored by tuning the statistical parameters of the RAFAL's output face, the signal frequency and the propagation distance in the water tank. The control and reproducibility of the measurements is therefore ensured. The influence of volume effects is especially studied, since the experiments were conducted in free field conditions. Results in terms of mutual coherence function (second-order moment) are presented ; a good agreement is found between the values of radii of coherence calculated using experimental and simulation data, as well as theoretical results. The evaluation of the complex pressure distribution highlights the relevance of the experimental scheme, since behaviors typical of the regimes of fluctuations (saturation and unsaturation) are found.
The Journal of the Acoustical Society of America
Articles you may be interested in Stochastic matched-field localization of an acoustic source bas... more Articles you may be interested in Stochastic matched-field localization of an acoustic source based on principles of Riemannian geometry
IEEE Journal of Selected Topics in Signal Processing
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.