How it works?

Overview
A-tag enables you to start acoustic monitoring of cetaceans, which you are interested in. A-tag offers multi-platform observations of cetaceans, originally developped to observe biosonar behavior by tagging on dolphins and porpoises in the wild. In recent years, A-tag has been applied for the acoustic transect to count the number of dolphins and porpoises, and for the long term stationed observation. A-tag can be attached on a rope towed from a boat, or on a pipe fixed beside a waterbreak, or on an animal using a suction cup. Application for passive acoustic monitoring, see this pdf file (ASA 2009, Portland, USA).
Enables counting number of phonating animals
A-tag can be used to count the number of animals acoustically. Two ultrasonic hydrophones of A-tag enables to record sound pressure at each hydrophones as well as the sound source direction calculated by the sound arrival time difference between two hydrophone. Identification of each sound source can be used to descriminate each phonating animal individually.
Simple operation
A-tag is a small and stand-alone system. The water registant body of A-tag sizes 21 mm in diameter and 108 mm in length + external stereo hydrophones. All of the data is stored in the flash memory of A-tag and is downloaded after you retrieve it. A-tag works up to 40 hours by CR2 lithium battery (standard type)and one month by two D cells for long-life stationed type (optional).
Open source
A-tag offers open source. For data analysis, Igor (Wavemetrics, AZ, USA) has been used. Source code of the noise reduction and identification of biosonar clicks is archived in this web page. You can download and modify the parameters to fit your animals and noise conditions.
See this page to download software, manual and sample data sets.
What can NOT do?
A-tag does not record sound waveform. It is event recorder of each pulse with received sound pressure level over the pre-set detection threshold level. Although the 70 kHz high-pass filter in A-tag reject the low frequency noise due to engine operation and water flow, heavy snapping shrimp noise in warm waters could reduce the detection performance of A-tag.

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