2023_programme: Directional monitoring of underwater sound fields using a glider

Back


  • Session: 17. Unmanned vehicles for underwater acoustic surveillance and monitoring
    Organiser(s): Alain Maguer
  • Lecture: Directional monitoring of underwater sound fields using a glider
    Paper ID: 1868
    Author(s): Giorli Giacomo, Cecchi Daniele, Garau Bartolome, Viola Salvatore
    Presenter: Giorli Giacomo
    Abstract: Monitoring the underwater soundscapes and their ambient noise levels is of crucial importance both for civilian and for military applications. Large scales and long-term monitoring are achievable by using unmanned vehicles, possibly creating widely dispersed and persistent networks of vehicles, equipped with acoustics sensors. For such tasks, measuring the directionality of the sound field becomes important to effectively collect and deliver information over large areas. By developing and integrating a 6-element compact volumetric array (cVAS) on a commercial SLOCUM G3 glider, we developed a system to estimate the directionality of the underwater sound field in the ocean in near real-time. The system simultaneously acquires the acoustic data and processes it to estimate the directionality of the sound as a function of the frequency using the Intensity Vector technique. Sound Exposure Levels histograms are then computed as a function of frequency and azimuth or elevation angles, respectively. The system was tested in the eastern Ligurian Sea during the Acoustic Technology Testing At Sea trial in October 2021. The glider was equipped with both the cVAS and oceanographic sensors, deployed from NRV Alliance, and programmed to patrol the study area to obtain the directional ambient noise products. In addition to this experiment, the glider was tasked to navigate at different ranges around a moored acoustic source deployed at a depth of 30 m programmed to transmit Linear Frequency Modulated (LFM) up-sweeps. The system successfully computed, compressed and transmitted the acoustic products in near real-time during the surfacings of the glider mission. An offline algorithm was also developed for detecting the LFM signals transmitted by the moored source and estimating their azimuth and elevation. Angles of arrival of the LFMs are estimated with an accuracy within 5 degrees.
  • Corresponding author: Dr Giacomo Giorli
    Affiliation: NATO STO CMRE
    Country: Italy
    e-mail:

Back