"A new intra-spectral monohydrophone range estimator and bioacoustic sparse coding for scaled submarine biodiversity"

Phd of Yann DOH
Director: Pr. Hervé GLOTIN, univ Toulon
co-director: Pr. Olivier ADAM, Univ Paris 6
co-supervisor: PhD Joseph RAZIK, univ Toulon
industrial co-supervisor: PhD Gilles Nolibe
Laboratory : UMR CNRS LSIS Toulon.
(Final manuscript will be available in february)

Abstract:

Acoustic waves show low dispersion due to the underwater propagation, compared to the propagation in the air. Some species of cetaceans communicate at long distance, others use their sound production for orientation. The goal of the scientific area called bioacoustics is to study animal species based on the analysis of their emitted sound. Their sounds can be used to detect, to classify and to locate the cetaceans. Recordings can be done with an passive acoustic array of multiple hydrophones, but this method is expensive and difficult to deploy. Thus, in order to scale this approach, we propose in this Phd thesis several original single hydrophone models to analyze these stationary or transient signals.

Firstly, we provide a new theoretical model to estimate the distance between the impulsive source (ex. biosonar of the cetacean) and the hydrophone. Our model, the Intra Spectral ATtenuation (ISAT), is based on the spectral signal alteration due to the underwater acoustic propagation, especially the differences in different frequency bands. We also approximated ISAT by an artificial neural network. Both models are validated on clicks emitted by sperm whales (Physeter macrocephalus) recorded by our sonobuoy BOMBYX and our data- acquisition system DECAV developed in collaboration with the National Park of Port-Cros (France) and the Pelagos sanctuary for the protection of marine mammals in the Mediterranean sea (France). The error (RMSE) measures on the recordings of the NATO test center in the Bahamas are about 600 meters, promising further real applications.

Secondly, we worked on the variations of the cetacean vocalizations using the sparse coding method. The encoding of the cepstrums by unsupervised learning of a dictionary shows bigrammic time changes of the songs of humpback whales (Megaptera novaeangliae). We validate this model on signals recorded in the Ste Marie Channel (Madagascar) between 2008 and 2014, through our network of hydrophones BAOBAB which is the first passive acoustic array deployed in the Indian Ocean. Our models are part of the Scaled Bioacoustics project (SABIOD, MI CNRS) and open perspectives for temporal and spatial scaling of bioacoustics.

Keywords:
underwater acoustics ; bioacoustics ; transient signals ; stationary signals ; large scaling ; single hydrophone ; source-receiver range estimation ; sparse coding ; humpback whale ; sperm whale ; Pelagos ; PNPC ; Madagascar.