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I am trying to learn the source of the sound in the spectrogram below. It has been recorded in early to late winter (January/February) on the shelf (25 m depth) off the US state of Georgia in the Western North Atlantic. There appears to be stacked harmonics that are frequency modulated. Audibly, they sound like they may originate from a marine mammal in my opinion. Any assistance would be appreciated. enter image description here

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    $\begingroup$ Can you add few more details about the recording? Can you link to an audio recording so we can listen to it? Also what time of day was it? $\endgroup$ Jul 27, 2022 at 20:18

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The fuzzy noise near 0Hz indicates instrument noise to me at first glance. I'd zoom in much further on that to see if there is a strong fundamental frequency.

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    $\begingroup$ I agree that there seems to be some low-freq noise which is coincident with the other sound, but surely we do already see a strong fundamental frequency, starting at ~150 Hz? $\endgroup$
    – Dan Stowell
    Jul 28, 2022 at 7:02
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    $\begingroup$ @DanStowell I agree the noise <150Hz is probably not the fundamental, but in my experience sometimes zooming in and changing the FFT size can make what looks like noise in higher frequencies actually resemble a super low tonal signal. Not that I am confident this is the case here, just the sort of due diligence I'd recommend to evaluate if this could be a tonal call versus noise. $\endgroup$ Jul 28, 2022 at 14:12

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