Example spectrogram and detections.

• Main Authors: William S. D. Wilcock (3749737), Rose S. Hilmo (4537330)
• Format: Still Image
• Language: unknown
• Published: 2021
• Subjects: Biological Sciences not elsewhere classified; Mathematical Sciences not elsewhere classified; Physical Sciences not elsewhere classified; studying marine mammals; passive acoustic monitoring; ocean bottom seismometers; many spurious solutions; increasing sampling rates; future experiments might; div >< p; balaenoptera musculus </; widely spaced network; false positives must; obtain tracks using; least 20 locations; earliest arrival time; different b calls; true positives; large network; b call; vocalize extensively; smooth paths; seismic frequencies; requiring groups; pacific northwest; obtained iteratively; minimize changes; localize calls; including constraints; important tool; follow within; first harmonic; feasible time; distance window; detecting harmonics; describe methods; calls identified; approaches lead; 15 hz; Pacific; Balaenoptera musculus; Blue whale
• Online Access: https://doi.org/10.1371/journal.pone.0260273.g002

(a) Spectrogram of 30 minutes of data with arbitrary scaling from station J53A starting at 03:30:30 UT on December 11, 2011, showing a sequence of strong Northeast Pacific blue whale calls. An earthquake is also apparent at ~1200 s as a vertical band of energy. (b) As for (a) but normalized by subtracting the median at each frequency and shown with a color scale for values that exceed the 90 th percentile value. (c) Four-minute segment of the spectrogram from (a) with A and B calls labeled. (d) Cross-correlation kernel that is tuned to the slope of the first half of the B call. (e) Recognition score (RS) for (c) with the minimum threshold of 2.2 shown as a dashed line. Three B calls are strong detections and both the A call and a faint feature early in the spectrogram register as weak detections.