Acoustic Laboratory for Marine Applications: Overview of the ALMA system and data analysis

The authors present a recently developed acoustic system (ALMA for Acoustic Laboratory for Marine Applications). ALMA was designed and used to address the topic of sound waves propagating in fluctuating oceans (especially coastal and shallow waters). Observing and understanding the underlying phenomena such as wavefronts fluctuations due to internal waves, scattering from the sea surface and/or bottom and their impact on sonar performance is the main long-term goal of this work. Several measurement campaigns were conducted and will be presented. They were carried out in the Mediterrannean sea in various conditions of water depth, season or type of emitted signals. An analysis of some of the acoustic and environmental data collected during the 2016 campaign will also be provided. The influence of temperature fluctuations is shown with calculation of the mutual coherence function and conventional beamforming.