<p>I've been trying to identify underwater sounds recorded in the eastern North Atlantic Ocean, at a 500 Hz sampling rate. I observed this low-frequency upsweep that was only produced once, but it shows high SNR and it is well-defined. However, I'm not sure if this is from a humpback whale (my first guess), because of the low frequency and only being produced once and by itself (no aliased parts of a song). Does anyone know what animal produces this type of sound? All the help is much appreciated! The first image is a close-up of the signal, and the second is one hour of recording around it.</p>
<p><img src="https://static.wixstatic.com/media/20b90c_8794f3f37cc0407a908d50f02e4130ad%7Emv2.png" alt="Here is a close-up of that signal" /></p>
<p><img src="https://static.wixstatic.com/media/20b90c_18dcf15f298c4b1b84db372cc063aaac%7Emv2.png" alt="Here is a spectrogram of 1 hour around that signal" /></p>

CC BY-SA 4.0
2024-07-21T11:02:40.783Z
I am no expert on this domain, but 20 seconds seems VERY long for an animal-produced upsweep, doesn't it? So I'd be inclined to think this may come from some mechanical source. But in either case, it's strange to see such a clear strong signal with apparently nothing else before/after.
Dan Stowell
CC BY-SA 4.0
2024-07-22T01:05:28.077Z
I'm not sure what these are, but wondering if there are some tonal signals around 50 and 20 Hz in the longer duration sample that might be a clue?
Brian Miller
CC BY-SA 4.0
2024-07-31T09:10:59.137Z
Thank you for your comments @DanStowell and @BrianMiller! Yes, the signal seems to be too long for a biological source, but it has such clear characteristics and high SNR... I guess it will remain a mystery for now... Before the upsweep, the  [tonal noise at 50 Hz seems to be shipping noise](https://static.wixstatic.com/media/20b90c_4ea34cc94a1d4ee0a4fe9c2876cf02e7~mv2.png) maybe? And after the upsweep,  [the low-frequency noise at 20 Hz might be instrumental](https://static.wixstatic.com/media/20b90c_993fc5dc754e4653b8f2011bb16a2e20~mv2.png). Doesn't seem to be fin whale signals...
Andreia Pereira
<underwater><species-identification>
What is the origin of this underwater low-frequency upsweep signal?
# What is the origin of this underwater low-frequency upsweep signal?

(Asked by: username_0 on 2024-07-19)

I've been trying to identify underwater sounds recorded in the eastern North Atlantic Ocean, at a 500 Hz sampling rate. I observed this low-frequency upsweep that was only produced once, but it shows high SNR and it is well-defined. However, I'm not sure if this is from a humpback whale (my first guess), because of the low frequency and only being produced once and by itself (no aliased parts of a song). Does anyone know what animal produces this type of sound? All the help is much appreciated! The first image is a close-up of the signal, and the second is one hour of recording around it.

![Here is a close-up of that signal](https://static.wixstatic.com/media/20b90c_8794f3f37cc0407a908d50f02e4130ad%7Emv2.png)

![Here is a spectrogram of 1 hour around that signal](https://static.wixstatic.com/media/20b90c_18dcf15f298c4b1b84db372cc063aaac%7Emv2.png)

**Tags:** underwater, species-identification

> **Comments:**
> **username_1**: I am no expert on this domain, but 20 seconds seems VERY long for an animal-produced upsweep, doesn't it? So I'd be inclined to think this may come from some mechanical source. But in either case, it's strange to see such a clear strong signal with apparently nothing else before/after.  
> **username_2**: I'm not sure what these are, but wondering if there are some tonal signals around 50 and 20 Hz in the longer duration sample that might be a clue?  
> **username_0**: Thank you for your comments @username_1 and @username_2! Yes, the signal seems to be too long for a biological source, but it has such clear characteristics and high SNR... I guess it will remain a mystery for now... Before the upsweep, the  [tonal noise at 50 Hz seems to be shipping noise](https://static.wixstatic.com/media/20b90c_4ea34cc94a1d4ee0a4fe9c2876cf02e7~mv2.png) maybe? And after the upsweep,  [the low-frequency noise at 20 Hz might be instrumental](https://static.wixstatic.com/media/20b90c_993fc5dc754e4653b8f2011bb16a2e20~mv2.png). Doesn't seem to be fin whale signals...  

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## 0 answers

