Body: <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>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-07-21T11:02:40.783Z
Comments.Text: 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.
Comments.UserDisplayName: Dan Stowell
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-07-22T01:05:28.077Z
Comments.Text: 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?
Comments.UserDisplayName: Brian Miller
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-07-31T09:10:59.137Z
Comments.Text: 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...
Comments.UserDisplayName: Andreia Pereira
Tags: <underwater><species-identification>
Title: What is the origin of this underwater low-frequency upsweep signal?
ThreadText: # 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 @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...  
  
  ---
  
  ## 0 answers
  
  