Inter-Pulse Estimation for Sperm Whale Click Detection

Sperm whales are characterized by the inter-pulse interval (IPI) of their vocalization, which is a function of the whales' size. In this paper, we propose a new methodology for detecting and extracting features from the IPI of sperm whale clicks. Our IPI estimator is based on the slope of the signal's phase spectrum, which takes on zero values whenever a pulse is observed. To manage outliers, we propose a segmentation algorithm for the choice of the most consistent IPI subset within a time buffer. Finally, a linear fit and standard deviation are calculated over the segmented subset. The proposed approach is demonstrated over data of recorded ambient noise (false alarm) and real sperm whale signals obtained in two designated sea experiments. Performance is compared with two widely used IPI-estimation benchmarks and with a waveform-based approach representative. Our results show that the proposed approach yields features with the highest separation.