1. D calls recorded on the tag hydrophone and tri-axial accelerometer.
D calls recorded on the tag hydrophone and tri-axial accelerometer. (A) Acoustic waveforms and spectrograms of two tonal downsweep calls (256-point FFT, Hamming window, 99% overlap). (B) Concurrent accelerometer readings from the tag's three orthogonal axes. (C) Cross-correlation functions between the acoustic signal and each of the three accelerometer signals. Peak coefficient (coeff) values for each cross-correlation are listed in the keys, indicating that the call on the left was deemed detectable on the y- and z-axes, while the call on the right was clearly detectable on all three accelerometer axes. These two downsweeps illustrate the variability in frequency range of D calls. Although the two acoustic signals are very similar in amplitude, the call on the right is associated with a stronger acceleration signal. For the call on the right, the aligned accelerometer signals from the x- and y-axes are offset by about 0.25 s, a pattern seen in many of the strongest D calls presumed to be produced by the tagged whale in deployment bm15_054a.
Mark R. Saddler et al. J Exp Biol 2017;220:
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