What WUZ that sound?

Minke whale

We’ve heard much about how little we know about the ocean; that “we know more about the surface of the moon than the bottom of the sea,” or that “less than 5% of the ocean has been explored.” Of course these are relativistic hyperboles that refer mostly what we can see – on the ocean surface; on maps that have been drawn of the ocean floor, or by way of the slimy catch (and by-catch) spilled out onto the decks of fishing boats. But what we have heard very little about is what we haven’t heard from the sea.

There are many stunning animal adaptations to the ocean’s dark abyss that look astonishing, but how might they sound? The OCR Sound Library has some remarkable sounds – such as the many odd sounds of the Minke whale, or the alien glissandos of the bearded seal.

We have an entire week of Arctic sounds provided to us by the Macaulay Library, the preeminent sound collection of Cornell University. When we were producing the spectrograms for this series we got the opportunity to spend a few weeks listening to the recordings. There are many sounds which have been identified on these Arctic recordings, but pretty often we would be startled by some bizarre, as-yet-undescribed sound coming from out of the acoustical abyss.

This sort of thing happens a lot in marine bioacoustics; some odd sound that comes and goes with no way to associate the sound with the source. It is by way of this that yet another bizarre sound has come out of the depths of the Marianas Trench recorded by a research team from Oregon State University – led by Principal Investigator Sharon Nieukirk.

Not being able to see the source, the team could only speculate that the sound emanated from a baleen whale – due to the low-frequency components, and probably some species of minke whale due to similarities in the high-frequency components of other confirmed recordings of minke whales.

At this time most recordings of marine biological sounds are taken from within the human-auditory band; and due to the high-density of acoustical data, the recordings are often band-limited to record within a frequency bracket that we can hear and identify (usually above 40Hz and below 4kHz).

Given the vicissitudes of Bioacoustic Niche Hypothesis it is likely that there are many more sounds outside of our typical acoustical listening window. And given the expansive variety of acoustical habitats in the ocean it is likely that there will be many more “bizarre” and unexplained sounds to discover.

Stay tuned!