In Autumn of 2012, many were complaining that they were, quite literally, sleepless in Seattle.
But rather than being the plot of a 1990s romantic comedy, this was the legitimate complaint of many who lived around the Duwamish River in West Seattle. It involved a strange, droning "hum" that, at times, had been keeping many residents awake at night.
Seattle's KPLU News reported that, "Residents think the sound could be coming from the nearby industrial cement plant, the slightly more distant Boeing Field, or big ships reverberating in the waters of the Duwamish, a heavy industrial waterway leading to Puget Sound."
Another suggestion was made by marine biologists with the University of Washington, who suggested that the Midshipman fish, a curiously toadish fish species capable of producing an odd, rattling mating call, might actually be the cause. It seemed possible, too, that the large ships in the Duwamish might actually have been amplifying the natural fish noises, which produced the strange hums (note, however, that this conclusion has been debated, as we'll discuss a bit later).
Amidst various anomalous sounds found in nature, it has long been held that certain fish species can create strange droning hums, or even sounds that have been likened the whirring song of the cicada. William R. Corliss, an American physicist and something of a latter-day Charles Fort (though, as Arthur C. Clark noted, a much more scientific version), had documented such reports within his Sourcebook Project, which produced a series of books that catalogued various anomalies in scientific literature.
One such report from 1854 reads as follows:
“One moonlit night in 1854, on board a steamer anchored near the Tavoy river (Tenasserim) we were struck by an extraordinary noise which appeared to proceed from the shore about a quarter of a mile off, or from the water in that direction. It was something like the sound of a stocking loom, but shriller, and lasted perhaps five or six seconds, producing a sensible concussion on the ear like the piercing scream of the cicada; and this gave an impression as if the vessel itself were trembling, or reverberating from the sound.” One of two Burmans on board said simply, the noise was produced by ‘fishes,’ but of what kind they did not describe. It was repeated two or three times.”
A similar report appeared in Popular Science Monthly three decades later:
“Lieutenant White, of our Navy, relates that, when at the mouth of a river in Cambodia in 1824, he and the crew of his vessel were struck by hearing extraordinary sounds, like a mixture of the bass of an organ, the ringing of bells, the guttural cries of a frog, and the tones of an enormous harp, which they heard around the bottom of their vessel. The interpreter said they were produced by a troop of a kind of fish.”
While the "fish theory" for the mystery hums remains a popular one, we must point out that researchers with the University of Washington who had initially suggested tanker hulls that might "amplify" fish songs later recanted, and expressed that such sounds could not be carried far enough inland to account for the purported hums, one of which had even been recorded using a smartphone. Joseph Sisneros, joined by grad students from the college, investigated areas of the Duwamish river with hyrophones, and determined there was "no evidence or data that the midshipman is present in West Seattle waters right now."
So what else might be the source of these mysterious humming noises?
A more recent investigation into Earth hums by geophysicists yielded yet another possible oceanic source for some of the noises. A study appearing in Geophysical Research Letters back in February, geophysicists have long classified certain constant "Earth hums" as a type of microseismic activity, which is believed to arise from movement of ocean waves along ridges and other geological formations along the ocean floor.
Expounding on the matter, we discuss the phenomenon thusly over at Mystery Booms:
[T]here are actually two phenomenon that are believed to be contributing to the mystery: massive ocean waves deep beneath the surface that comb along bottom slopes, producing seismic waves in the process, paired with collisions between ocean waves that occur elsewhere. The resulting microseisms can range from 3 to 10 seconds; while these are often reported, seismic periodicity lasting up to nearly 300 seconds has also been documented.
Of that last line appearing above, it is worth noting that IFL Science actually reported the upper ranges of seismic activity as being merely "13 to 30 seconds", while the abstract for the study (which can be seen here) states in the title that periods reaching "300 s" have been reported, but notes that they remain a matter of some debate.
This new information, which combines multiple sources that have long been suspected of anomalous seismic phenomena, causes one to wonder whether some reports of "mystery hums" might indeed result from wave activity deep beneath the ocean. And as for "fish songs"? Well, you're probably more likely to see one flying than to hear one singing... at least depending on how far inland you may be.