pone.0227392.g002.tif (3.82 MB)

Audio signal strength versus distance.

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posted on 16.04.2020, 17:35 by Rogier Landman, Jitendra Sharma, Julia B. Hyman, Adrian Fanucci-Kiss, Olivia Meisner, Shivangi Parmar, Guoping Feng, Robert Desimone

A. Wave (upper row) and spectral intensity (bottom row) from one voice recorder as seen in Audacity, the software we used for annotation. Shown is a recording of a single trill call played on a speaker at various distances. There is a steep fall off between 0.05 m (the approximate distance between the animals’ mouth and the recorder) and 1 m. Beyond 1 m, fall off is less steep. Besides lower intensity, the spectrogram also shows less detail, such as the sinusoidal frequency modulation that is typical of trill calls. B. Animals were video-recorded from overhead. A video frame taken at the onset time of a trill call shows two animals wearing voice recorders marked pink and green. The inter-animal distance is 549 mm. C. Spectrograms of the call from the two voice recorders show a difference in intensity that can be used to infer which animal called. This call is attributed to animal 1 (green). D. A video frame with inter-animal distance 76 mm. E. Spectrograms show higher intensity for animal 2 (pink), to whom the call is attributed.