Greetings Bioacoustics Community! I am looking for a bit of input regarding a set of low-frequency variable calls that are likely of baleen whale origin. The data were collected in April of 2023 off the coast of Oregon over a period of several hours during which the frequency-modulated calls repeatedly occurred. Most of the calls are within a 30 - 90 Hz bandwidth, and vary in duration from 0.9 seconds to approximately 3 seconds (though several were slightly longer up to 4.3 seconds). I am aware the frequency modulated calls can be a shared vocal type among baleen whales, but the nature of some of these "m-shaped" calls are very distinct. There are NO audible co-occurring humpback vocalizations and no other species detected after the end of this set of calls. Any thoughts on what this Pac NW species may be? I cannot at this time provide audio files due being currently restricted but can add these at a later data when cleared.

Image Description: Spectrogram of low-frequency (0-200 Hz) bandwidth with several examples of calls within annotation boxes. The spectrogram parameters include Hann window, 256 FFT, and 90 percent overlap. Files have a 500 Hz sampling rate. enter image description here enter image description here enter image description here


1 Answer 1


Those look like they could be blue whale non-song sounds, but it's difficult to know with any certainty without any further context.

These type of blue whale calls are uncommon, so have only been sporadically reported, and have been called a few different names over the years.

For example: Rankin et al (2005) refers to similar sounds as 'uncommon short-duration FM vocalisations (see their Figure 3). Oleson et al (2007) calls them D/AM/FM calls, and also indicates that they are uncommon (their Figure 3 as well). Berchok et al (2006) hints at their existence among the more typical 'downswept' calls which they call 'audible downsweep call types' (their Figures 4 & 13). I've noticed similar calls recorded on sonobuoys in the vicinity of frisky Antarctic blue whales, but my data have not yet been published anywhere other than grey-literature cruise reports (O'Driscoll & Double 2015) Since that cruise report doesn't seem to show up on a google search, I've included the relevant figure here.

Figure 16 from O'Driscoll & Double 2015: Variety of forms of FM calls of Antarctic blue whales

If you get clearance to share the files, I'd be happy to take a closer look -- just drop me an email with the files, or a link to the download.




  • Berchok, C. L., Bradley, D. L., and Gabrielson, T. B. (2006). St. Lawrence blue whale vocalizations revisited: Characterization of calls detected from 1998 to 2001. Journal of the Acoustical Society of America 120, 2340. doi: 10.1121/1.2335676.
  • O’Driscoll, R., and Double, M. (2015). Voyage Report TAN1502 New Zealand-Australia Antarctic Ecosystems Voyage. Wellington, New Zealand: NIWA Client report WLG2015-21.
  • Oleson, E. M., Calambokidis, J., Burgess, W. C., McDonald, M. A., LeDuc, C. A., and Hildebrand, J. A. (2007). Behavioral context of call production by eastern North Pacific blue whales. Marine Ecology Progress Series 330, 269–284. Available at: http://escholarship.org/uc/item/5xk9k7bp.pdf.
  • Rankin, S., Ljungblad, D. K., Clark, C. W., and Kato, H. (2005). Vocalisations of Antarctic blue whales, Balaenoptera musculus intermedia, recorded during the 2001/2002 and 2002/2003 IWC/SOWER circumpolar cruises, Area V, Antarctica. Journal of Cetacean Research and Management 7, 13–20.
  • $\begingroup$ Thanks so much for your input Brian! Will definitely ping you with files when cleared - appreciate it! $\endgroup$
    – LizFerg
    Oct 17, 2023 at 4:15
  • $\begingroup$ Cool. If it might help, I'd be happy to send you some clips from my recordings (all of which are essentially publicly available) so you can start assessing similarity without having to wait for clearance to send me anything. $\endgroup$ Oct 18, 2023 at 6:19
  • $\begingroup$ Thanks Brian I will email you! $\endgroup$
    – LizFerg
    Oct 19, 2023 at 16:03

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