Localization with Time-Reversal Acoustics – LORETA

The LORETA project (LOcalisation par Retournement Temporel Acoustique) is a research initiative with balanced contributions from the ISL and the Laboratoire de Mécanique des Fluides et d’Acoustique (LMFA). The general purpose of the project is to pursue the development and evaluation of the time-reversal localization system. The project is based on 59 months of work and lasts 30 months. It will gather the theoretical, modelling and experimental skills of six permanent researchers and a post-doc.
A first, upstream research goal is to document the propagation of transient sounds in the presence of obstacles and ground effects. Indoor acoustic measurements will be coupled to a Schlieren imaging system. The observations will be compared to an up-to-date numerical modelling of the sound propagation in the time domain. Outdoor propagation measurements will also be performed. The so-formed dataset may be distributed.
The second research task is aimed at developing and testing reduced numerical solutions in order to simulate sound propagation in the localization system. Existing models will be compared with the observational data acquired in the upstream research task. The evaluation will account for reliability and computational request. The selected solutions will be integrated in the sound propagation model used for localization. The model will be evaluated in a reference outdoor, urban scenario.
The third research task is to quantify the performance of the time-reversal localization system within the above reference scenario. Specifically, we will investigate the performance sensitivity to (i) modulations of sound propagation induced by the atmosphere, (ii) the location and number of deployed acoustic sensors, and (iii) the refinement of the sound propagation model relative to the computational request.

Finally, specific dissemination and exploitation initiatives are proposed toward the scientific and technical communities involved with the outdoor sound propagation and the localization of acoustic sources such as gun shots. With these dual purposes and with the innovative scientific goals, the proposed research project particularly fits with the scientific objectives of the ASTRID call.

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Localizing transient acoustic signals has a dual interest. It may contribute to area surveillance. It also constitutes a protection against snipers. For these reasons, acoustic localization systems have been developed and satisfactorily evaluated in open outdoor environments. In urban environments though, the ground surface and the surrounding buildings strongly modulate the acoustic propagation, through reflection, masking and/or diffraction of the signal. These modulations dramatically degrade the performance of standard systems for acoustic localization.
The challenge is to conceive and develop an innovative system which can integrate the complex propagation features caused by urban environments. The French-German Research Institute Saint-Louis (ISL) has developed a preliminary acoustic localization system, based on the concept of time reversal. The principle is to measure the transient signal at various locations in the urban environment, reverse the chronology of signals, and simulate the propagation of the reversed signals within the synthetic urban environment. The maximum interference gives the source position. The system has been satisfactorily tested in idealized frameworks. The tests also pointed the necessity of a more exhaustive and efficient description of signal propagation in the urban environment.
The LORETA project (LOcalisation par Retournement Temporel Acoustique) is a research initiative with balanced contributions from the ISL and the Laboratoire de Mécanique des Fluides et d’Acoustique (LMFA). The general purpose of the project is to pursue the development and evaluation of the time-reversal localization system. The project is based on 59 months of work and lasts 30 months. It will gather the theoretical, modelling and experimental skills of six permanent researchers and a post-doc.
A first, upstream research goal is to document the propagation of transient sounds in the presence of obstacles and ground effects. Indoor acoustic measurements will be coupled to a Schlieren imaging system. The observations will be compared to an up-to-date numerical modelling of the sound propagation in the time domain. Outdoor propagation measurements will also be performed. The so-formed dataset may be distributed.
The second research task is aimed at developing and testing reduced numerical solutions in order to simulate sound propagation in the localization system. Existing models will be compared with the observational data acquired in the upstream research task. The evaluation will account for reliability and computational request. The selected solutions will be integrated in the sound propagation model used for localization. The model will be evaluated in a reference outdoor, urban scenario.
The third research task is to quantify the performance of the time-reversal localization system within the above reference scenario. Specifically, we will investigate the performance sensitivity to (i) modulations of sound propagation induced by the atmosphere, (ii) the location and number of deployed acoustic sensors, and (iii) the refinement of the sound propagation model relative to the computational request.
Finally, specific dissemination and exploitation initiatives are proposed toward the scientific and technical communities involved with the outdoor sound propagation and the localization of acoustic sources such as gun shots. With these dual purposes and with the innovative scientific goals, the proposed research project particularly fits with the scientific objectives of the ASTRID call.