Bioacoustic monitoring, such as surveys of animal populations and migration, needs efficient data mining methods to extract information from large datasets covering multi-year and multi-location recordings. Usually, the study of the humpback whake songs is based on the classification of sound units, notably to extract the song theme of the singers, which might signify the geographic origin and the year of the song. Most of these analyses are currently done with expert intervention, but the volume of recordings drive the need for automated methods for sound unit classification. This paper introduces a method for sparse coding of bioacoustic recordings in order to efficiently compress and automatically extract patterns in data. Moreover, this paper proposes that sparse coding of the song at different time scales supports the distinction of stable song components versus those which evolve year to year. It is shown that shorter codes are more stable, occurring with similar frequency across two consecutive years, while the occurrence of longer units varies across years as expected based on the prior manual analysis. We conclude by exploring further possibilities of the application of this method for biopopulation analysis.
Odontocetes modulate the rhythm of their echolocation clicks to draw information about their environment. When they approach preys to capture, they speed up their emissions to increase the sampling rate of "distant touch" and improve information update. This global acceleration turns into a "terminal buzz" also described in bats, which is a click train with drastic increase in rate, just as reaching the prey. This study documents and analyses under human care bottlenose dolphins' echolocation activity, when approaching non-alimentary targets. Four dolphins' locomotor and clicking behaviours were recorded during training sessions, when sent to immersed objects pointed by their trainers. Results illustrate that these dolphins profusely use echolocation towards immersed non-alimentary objects. They accelerate click emission when approaching the target, thus displaying a classical terminal buzz. However, their terminal buzz slackens off within a quarter of second before the end of click train. Typically, they decelerate to stop clicking just before they touch the object using their rostrum lower tip. They do not emit clicks as the contact lasts. In conclusion, when exploring inert objects, bottlenose dolphins under human accelerate clicking like other odontocetes or bats approaching preys. Bottlenose dolphins' particular slackening-off profile at the end of the buzz shows that they anticipate the moment of direct contact, and they stop just as real touch relays distant touch of the object.
les baleines à bosse mâles émettent des vocalises organisées et, pour certaines, répétées formant ainsi le leitmotiv d'un chant. Principalement, dans le but de mieux appréhender le comportement de ces baleines et notamment les interactions entre individus (mâle/mâle, mâle/femelle), plusieurs études sont actuellement menées sur ces chants. Dans cette étude, nous nous intéressons aux unités sonores, vocalises séparées par 2 silences, qui composent ces chants, à leurs récurrences, et à leurs structurations. Cependant, tous ces paramètres dépendent de l'année et du lieu d'enregistrement. Des travaux antérieurs ont souligné la nécessité de méthodes objectives pour la classification de ces unités sonores. L'analyse détaillée des vocalisations a montré que les caractéristiques d'une unité peuvent changer brusquement pendant toute sa durée, ce qui les rend difficiles à caractériser et à grouper systématiquement. Cet article propose un codage parcimonieux des chants afin de déterminer leurs composantes stables de celles qui varient, pour différentes échelles de temps. Une définition de la complexité du code est également proposée afin de séparer les composantes Traitement du signal-n o 3-4-5/2013, 219-242
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