Figure 7. Example of unknown echolocation clicks likely produced by beaked whales.

Figure 7a shows a spectrogram of the ‘double click’. Recording was made at 500 m depth. Figure 7b represents a spectrum of the click (solid line) and the background noise level at the time of the recording (dotted line). Spectrogram parameters used to generate plots: frame size 32 samples (0.16 ms), FFT size 128 samples (0.64 ms), overlap 94% (0.15 ms), and Hamming window, for a spectrum filter bandwidth of 24.6 kHz. Data were high-pass filtered at 10 kHz prior to processing.