Signal Images Physique
Team manager : Jocelyn CHANUSSOTCornel IOANA

Research Areas

Signal and wave propagation

Numerous problems still prevail in underwater acoustics for systems deployed in coastal and shallow depth environments, where the propagation phenomena are still more complex and will have a very important impact on all acoustic devices  for the transmission, communication and, generally, the detection of acoustic signals. In order to better comprehend the issues related to the detection, an priori description of the small scale physical phenomena is therefore paramount. Our research studies are following three directions:

. High resolution oceanic tomography and acoustic barriers

Détection de cible sous-marine

Using two sources-receptors networks and a signal processing tools adapted to this configuration, we have developed an efficient and robust oceanic tomography method, based on times of arrival and sensitivity kernels. Other more interesting approaches consist in taking into account the angles or even the total field in order to achieve the inversion. The research efforts are concentrated on:
- The extraction of features related to the sound velocity in water (time of arrival, source and receptor wave angles and amplitudes) using high resolution methods;
- Develop new inversion procedures based on combinations between the time of flight, source and receptor wave angles, and using sensitivity kernels adapted to each new feature;

- The aforementioned methods are validated by the study of experimental data recorded at sea, and by reduced scale tests carried out at ISTerre, Grenoble. Moreover, relying on a configuration of antennas (sources and receptors) used for tomography, we are also developing methods for localizing emitting sources based on amplitude variations of waves affected by a potential target in the environment.

. Natural environments observations using passive acoustics

The monitoring of natural environments for communication, surveillance and responsive purposes is a sensible issue having strategic and social stakes. This is why it is essential to dispose of means for long term, continuous and real time monitoring for this environments.
In the case of large bodies of water (oceans, coastal regions, lakes, rivers), the monitoring can be done using the technique of listening  the sounds made by the environments, in order to extract knowledge over the sources producing these sounds (detection, classification, localization) and on the carrier channel properties (passive tomography). This "acoustic" knowledge of the environment leads to an "ecological" knowledge.
In order to contribute to the monitoring of these natural environments by passive acoustics, the signal processing tools aiming at analyzing the contents of these sounds have to be invented. These tools are adapted to the different classes of signals generated by an environment: stationary stochastic processes, frequency modulations and short transients.

. Ultra low frequency waves

The input acquired on the propagation of LFW and the techniques used for extracting the information from the recorded signals allowed the development of systems for environment identification and source localization, using a sensor antenna. Now the objective consists in investigating the case where only a sensor is available. In this case, we have achieved the source localization and developed a method for environment identification in the case of complex sources (non impulse, less wide band), because existing methods do not allow the solving of these issues. 

GIPSA-lab, 11 rue des Mathématiques, Grenoble Campus BP46, F-38402 SAINT MARTIN D'HERES CEDEX - 33 (0)4 76 82 71 31