Figure 4From: Underwater Broadband Source Localization Based on Modal Filtering and Features ExtractionULF sources: waveforms and spectrums. The first signal (a) and (c), denoted as ULF-1, is a flat spectrum transient. The second signal (b) and (d), denoted as ULF-2, is a broadband comb-type ("4 hills" spectrum) transient.Back to article page