Abstract
Cetacean monitoring is key to their protection. Understanding their behavior relies on multi-channel and high-sampling-rate underwater acoustic recordings for identifying and tracking them in a passive way. However, a lot of energy and data storage is required, requiring frequent human maintenance operations. To cope with these constraints, an ultra-low power mixed-signal always-on wake-up is proposed. Based on pulse-pattern analysis, it can be used for triggering a multi-channel high-performance recorder only when cetacean clicks are detected, thus increasing autonomy and saving storage space. This detector is implemented as a mixed architecture making the most of analog and digital primitives: this combination drastically improves power consumption by processing high-frequency data using analog features and lower-frequency ones in a digital way. Furthermore, a bioacoustic expert system is proposed for improving detection accuracy (in ultra-low-power) via state machines. Power consumption of the system is lower than 30 μW in always-on mode, allowing an autonomy of 2 years on a single CR2032 battery cell with a high detection accuracy. The receiver operating characteristic (ROC) curve obtained has an area under curve of 85% using expert rules and 75% without it. This implementation provides an excellent trade-off between detection accuracy and power consumption. Focused on sperm whales, it can be tuned to detect other species emitting pulse trains. This approach facilitates biodiversity studies, reducing maintenance operations and allowing the use of lighter, more compact and portable recording equipment, as large batteries are no longer required. Additionally, recording only useful data helps to reduce the dataset labeling time.
Highlights
Every day, more than one hundred animal species disappear in the world
It is important to note that this paper only focuses on the ultra-low power part of the wake-up system as well as the dynamic expert rules-based tuning algorithm: Section 2 presents the ultra-low power cetacean click detector, Section 3 describes optimization of the algorithm using experts rules and automatic gain control
Power consumption impact of these expert rules and automatic gain control is low: current is increased by 4.5 μA, mainly because of a timer used for evaluating pulse and inter-pulses duration has been activated
Summary
More than one hundred animal species disappear in the world. Since the. This article focuses on one of the most relevant technique: acoustic monitoring of animals emitting sound pulses, bursts or frequency chirps [1]. This category involves several species, from the smallest such as insects or birds emitting trains of voiced pulses [2,3] to the largest mammals. In contrast with global issues, this can be locally avoided by detecting cetaceans in real time: some boat and whale collisions could be prevented if relevant alerts were sent to in time This is the main purpose of this work, as well as monitoring them accurately to gather a better knowledge about them. Detection accuracy is further improved by using an expert rules system to reject false-positives
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