A generic system for the automatic extraction of narrowband signals of biological origin in underwater audio

Narrowband acoustic signals occur prominently in underwater environments and are commonly used in the identification of the vocalizing species. Disparate ad hoc systems have previously been developed for the detection or recognition of several forms of narrowband signals produced by specific species of marine mammals. We present a generic system, based on post-processing of spectrograms, for the automatic extraction of time-frequency contours of narrowband signals produced by marine mammals. A two-phase approach is proposed where the first phase is based on an image-processing technique for detecting intensity ridges and the second phase is a Bayesian filtering approach for tracing the trajectory of detected ridge apices. The choice of algorithm parameters and conditionals are backed with theoretical motivations and are geared to result in a generic (non-targeted) system. In comparison to an existing method, using publicly available pre-annotated recordings containing four species of dolphins, our system ...