As promised in the last post, today I’m putting forward my three best hypotheses for a solution to the mystery behind the West Seattle Hum. They’re ranked in what I consider the most likely order of plausibility, from least to most
Disclaimer: I see some people from Seattle are visiting. I should make it clear that I live in Australia and my speculations on this matter are based on my readings of the West Seattle blogs & forums, on researching of map data and tide and astronomical tables, and on my expertise as a professional sound worker. I have tried to be as accurate as I can, but am open to any corrections of errors or omissions that I may have made.
The Cause of the Hum: Speculation #1
The map I made in the last post throws up one element that might give us a clue to what’s going on with the Hum: some indication for direction of the origin of the sound. A direction, if it can be established, would indicate a point source that could be tracked down. The directional information on my map, slight as it might be, indicates a source position which would tally closely with the location of the Lafarge gypsum works & shipping yards on the Duwamish river, which was suggested by numerous commenters as a likely candidate for the Hum. It is extremely possible that some piece of machinery – a fan, an air conditioner or an electrical transformer perhaps – could make a noise like that recorded by Julie Schickling. According to the West Seattle blog, when Lafarge was approached about the sound, a representative from the company didn’t dismiss out of hand the idea that the Hum might be coming from them, but said also that they had no idea what it might be. It seems to me that a loud point source would be reasonably easy to locate though, and at least one commenter who followed this line of enquiry seems certain that the Lafarge plant is the culprit:
‘We finally were fed up with the infernal noise and went out to look for it. From Highpoint to Highland Park to South Seattle Community College to Pigeon Point and then finally West Marginal. The noise is clearly coming from the Lafarge Cement plant.’ ~ said R0b0, on the forums
But another resident, on attempting to track it down noted that the noise diminished as she approached the plant and seemed instead louder downriver to the South:
‘We did drive down a couple of nights ago to try and find it and we thought it might be coming from a ship that was moored off the Northland pier on the Duwamish…. We did drive further north toward the cement plant, but it seemed quieter there.’ ~ said Kay K
A few commenters on the West Seattle blog and the forums suggest they will make a video of the Lafarge plant to demonstrate their convictions, but so far no such video corroboration has materialized. Since this would seem to be an extremely easy thing to accomplish given the proliferation of phones & cameras with video capability, the absence of any such evidence (which one would think might be quite unequivocal) is puzzling.
If the Hum is a mechanically generated sound, though, the biggest question is how it might be heard right across West Seattle without the point source being deafening. And not just heard, but heard loudly in places as far away as Lincoln Park. Radiated sound, under normal circumstance, is a pretty straightforward thing. Soundwave radiation follows the Inverse Square Law, which says that the intensity of a sound is inversely proportional to the square of the distance from the source. Using this law we can quite easily calculate how loud a sound would be at Lincoln Park if generated at Lafarge. If we assume that the original sound is 115 decibels, which is VERY loud (around the kind of level you might experience at a loud rock concert) then by the time it traverses the 4.5k (3 miles) to Lincoln park, it has decreased to 42 decibels. That’s really quiet – somewhere between a subdued conversation and a whisper. That’s also assuming that there’s nothing in the way – that is, there would need to be a direct line of site between Lincoln Park and the Lafarge plant to get that even that meagre level of sound. I can tell easily from looking at the Google terrain map that this is not the case. I think I could confidently say that under normal circumstances, a resident in Lincoln Park could not hear sounds emanating from the Lafarge area. To add to the problem, for people living closer to Lafarge, there would be no question whatsoever about the location of a noise of 115db (just like you would know without a shadow of a doubt if there was a rock concert happening at the end of your street).
As bad as this looks for the hypothesis that the sound comes from the cement works, there is in fact an explanation that might come some way towards creating a plausible mechanism that could carry the sound across West Seattle.
If the conditions over the area are such that, on the mild, clear nights, an inversion layer forms, it is entirely possible that sound travelling up from somewhere in the direction of the Lafarge plant could be reflected back down into the suburbs. Inversion layers are much more likely to form in the early hours of the morning as the surface temperature cools, so this would suggest the Hum should be heard well after midnight – probably around 2 – 4am. This does fit with many of the reports on the West Seattle blog. Obscure kinds of atmospheric effects could also be at work, amplifying the sound in odd and uneven ways across the district.
This scenario would further help to explain the diffuse, directionless nature of the sound and you could also reasonably expect similar kinds of phasing and beating effects to Ms Schickling’s recording. Additionally, it would be in keeping with the drifting in volume effects noticeable on that recording.
But I reiterate – this explanation requires a substantially loud point source which would not be that difficult to locate with a decibel meter and and even mildly determined effort.
The Cause of the Hum: Speculation #2
In the NPR story that I mentioned last post, Dr. Andy Bass, from Cornell University, tells listeners that when Midshipman fish are mating:
Individual males build a territory, if you will, under a rock shelter. And from that rocky shelter, they produce that hum advertisement call to attract females to their nest.
In the YouTube video in the last post, that behaviour is clearly observable: the fish is taking a position in a hollow under a ledge and making its noise. From an acoustic point of view there is a compelling reason it might want to do this – a small cave under a rock would provide a kind of resonant cavity with a soundboard, helping to amplify its calls. Now, I’m certainly not an expert on the Midshipman fish, but let’s suppose that, like insects or frogs, the individual that makes the loudest sound has the best chance of attracting a mate. We would, therefore, have a situation driven by evolution where the Midshipman fish actively seeks out places that help amplify its sound. And each generation would tend to favour the fish that gets louder. So what we would have is a two kinds of evolutionary pressure at work – one on the fish’s physiology, and the other -significantly I think – on its behaviour. In the natural world, this is going to be a kind of self-regulating mechanism, since a fish only needs to be louder than the next loudest fish and no more – it’s a balance between loudness and energy expenditure and locating the most effective rock ledge available. Around Seattle, though, the fish has extra competition: boats, ferries, industrial racket – all possibly creating sounds of a similar nature to its own mating call. So a Midshipman fish quite conceivably faces an evolutionary imperative to outcompete human-made sounds in addition to the calls of other Midshipman fish.
If this is the case – and I think it’s a supposition on par with the same phenomenon being recorded with birds – then humans may have provided a problem for the Midshipman fish around West Seattle. As luck would have it, though, I think humans may have also been the engineers of a solution to the fish’s problem, and the creators of a new one of their own.
I have only been to Seattle once, in transit, so I can’t say I’m familiar with the city at all. But right now I’d just love to go to the Lafarge container dock on the Duwamish and take a look at it. I’m betting that underneath those big landings that flank the river, are hundreds of nooks and crannies with cavities and sounding boards – Midshipman fish heaven. Better than rock, they’d be roofed with wood and concrete and metal, materials that resonate in an excellent fashion, given favourable frequencies.
I want to remind you of a few of comments I featured from the West Seattle blog in the previous post:
‘I’m familiar with this noise too and think it is coming from the sewers. Next time you hear it go to a storm drain and see if it is louder’ ~ said mmd.
‘What’s weird is it sounds loud inside and when you walk out it seems quieter’ ~ said DRW
‘Reminds me of a didgeridoo…’ ~ said steph
‘Seems to change pitch/intensity in a slow rolling pattern, makes me wonder if we’re hearing an interference pattern between multiple sources.’ ~ said ben
When I listen to the recording made by Julie Schickling and compare it to dry recordings of the Midshipman made by Cornell University, I can hear immediately that there are (at least) five distinct audio phenomena at work in Ms Schickling’s recording that differentiate it from the latter. Phasing, resonance, ‘beating’ and reverberation, and a distinct swelling and abating of the sound, which is probably an effect of changing air pressure, or breeze direction. The first four of these can be commonly found in one circumstance: inside a tube or other long resonating cavity. It’s exactly the kind of effect you get when you play a didgeridoo, for example: the initial sound vibration interacts with itself to resonate, phase and create harmonics.
Now I’m not suggesting that the Midshipman fish has evolved to the point where it can play the didgeridoo, but are there other tube-like cavities to which it might have access? Long cement tunnels filled with air, say? Like… stormwater drains?
This, then, is what I consider the next most plausible hypothesis for the West Seattle Hum: as the weather warms up coming into Spring, the male Midshipman fish starts seeking out habitat suitable for its mating rituals, around the coast of West Seattle and especially right down along the Duwamish river near the Lafarge container docks. What it’s looking for are large cavities with exceptional resonant properties. These could be concrete piers, metal boat hulls, wooden wharves or even culverts and drains on the river frontage. I’m betting that there are numerous stormwater outlets that go down to the Duwamish, and probably others on the Western coast as well. These possibly even run submerged into the water. The stormwater drains undoubtedly reach everywhere back up underneath the suburbs of West Seattle. When the fishes start producing their mating call, the vibrations from the resonant cavities in the river and near the drains, begin to generate sympathetic resonances in the air columns in the stormwater tunnels, amplifying the sound, but also very importantly, carrying it up under the streets, where it echoes out from any opening to the outside. It would be formless and directionless – seeming to come from everywhere at once, even, perhaps, being louder inside a house than out. Because it’s being channeled in the drains, in some areas you might hear it clearly and loudly, while in others – even quite close by, you might not hear it at all. The sound being pushed through multiple tubes and tunnels would surely phase with itself and reverberate, and surge as the air pressure changed, reacting with itself to create harmonics such as we hear in Julie Schickling’s recording. The sheer amplification potential of this massive resonant chamber under West Seattle would spur all the fish in the area into competition, rather than exciting just a few proximate neighbours, as would happen in a completely natural environment. As anyone who has recorded frogs or insects knows very well, these creatures in competition can achieve almost deafening levels of sound. It is, in my view, entirely feasible that something like this could be happening in this human-altered Midshipman fish environment.
I want to point out here another factor which may be in play and hasn’t been noted elsewhere: The Labor Day weekend this year, when most of the recent incidences of the Hum were noted, just happened to coincide exactly with a full moon (full moon Aug 31, 99% Sept 1, 98% Sept 2, 94% Sept 3). I can’t say if it’s true of the Midshipman (biologists?) but I do know that the full moon spurs on the mating cycles of many sea creatures. Seattle is also currently experiencing a period of unusually extended dry weather, so the nights over the time of the reportings were clear and mild and the moon would have been prominent in the night sky. Maybe over the Labor Day holiday there was a veritable Midshipman fish orgy going on.
‘I’ve been in Sunrise Heights for 50 years and just started hearing this a couple of years ago. I can tell you that I hear it almost monthly, toward the last weekend of the month’ ~ said LisaH, on the forums.
Or just maybe, Lisa, on every full moon…
The best thing about the Midshipman proposition is that it is trivially easy to test. Next time the sound starts up, someone just needs to go down into the drains. I should think it would be immediately obvious if the sound is coming from there. It would be way louder than anywhere on the streets.
I think also that there are some predictions that can be made if it is the Midshipman fish, and if it is coming from the stormwater system:
1: It’s unlikely the sound will be heard when it’s very windy, from any direction: wind will tend to interfere too much with the air pressure to allow resonance to form well. Mild to warm still conditions would work best.
2: It’s unlikely the sound will be heard through the colder months: the fish don’t make the noise unless mating. You’d certainly never hear it in Winter.
3: It’s unlikely the sound will be anywhere near as prominent during the day, even on quiet early mornings: the fish mate at night.
4: The next clear night with a full moon would be the time to go out with a recorder and get your evidence.
The Cause of the Hum: Speculation #3
My third, and final, speculation on the cause of the West Seattle Hum will, I anticipate, be the least popular of all three among the district’s residents, but I believe it is the most plausible of all. ‘Less popular than the fish!??’ I hear you cry. Well, yes. Speculation #3 is that there is no Hum. Well, at least, there is no one thing that’s causing ‘the’ Hum.
When you have a lifelong interest in weird shit, as I do, you get quite familiar with certain kinds of phenomena that occur time and time again in slightly different guises. One of these recurring phenomena is filed under the heading ‘Mass Delusions & Hysterias’. Now this is not to imply that the residents of West Seattle are somehow mad, or even that people who have heard something are imagining it. But reading the comments on the West Seattle blog, you do feel, as I said at the start of my story in the last post, that all these folks may not be describing exactly the same thing. Some, for example, say the Hum is low pitched – that’s not how I would describe the recording made by Julie Schickling (which other commenters say is exactly the sound they have heard). Some describe the Hum as ‘a grinding sound’, while others say it’s like tinnitus. Some describe it like the sound of trains, others say it’s a noise like ferries, and yet others, helicopters, vacuum cleaners, and idling cars. These are all very different sounds.
Further, the researchers from Washington University, who proffered the Midshipman fish explanation, have not been able to establish their hypothesis as plausible mechanism after attempting to get a sound recording of it (although I do feel I must point out that one failed recording expedition is not any kind of proof that there are no Midshipman fish in the Duwamish or off the coast of Seattle at this time – it only demonstrates that there was no Hum on the single night that they made their recordings).
Then we have this rather… perplexing… situation as reported by the Seattle Times:
The [West Seattle] blog’s Patrick Sand said the sound was active for two or three days but stopped after people wrote about it. “That seems to have scared off the noise,” he said.
Whoa! Hang on a second there. So, people heard the sound in spades over the Labor Day weekend, but it suddenly disappeared entirely when under scrutiny? That, my friends, is a major red flag in favour of the mass delusion phenomenon.
In essence, it works like this: it’s a holiday weekend, nice weather. People are possibly out & about a bit more, staying up later than usual. In the early hours, some irritating humming noise starts up – it’s a street sweeper, but you’ve not really been awake at this hour much before and never heard one, so you can’t place the sound. Next day you mention it to a friend. ‘Isn’t that the damn Hum people were talking about back in ’09?’ asks your pal. Maybe it is, you think, and tell someone else over coffee. ‘Oh, I heard that last night!’ says your co-worker, who is actually talking about the transformer in the substation at the end of the street, which they’d not really noticed until now. Then you log on to the West Seattle blog and ask if anyone else has heard ‘The Hum’. Before too long, lots of people recollect that, yes, maybe they heard it too…
If you haven’t already, go to the blog now and read down the comments from the beginning with that thought in mind. You’ll keep tripping over observations like these:
‘I think it may be the power of suggestion. Now in Upper Fauntleroy, with a window open to the east-facing back yard, I’m thinking I hear something ambient out there.’ ~ said WSB on the forums.
‘This is not the same hum I’ve noticed in the past.The old hum seemed to be during daylight hours and seemed to come in from the West.’ ~ said old timer
‘This is incredibly weird, because I live at the top of Highland Park Way, and so you’d think based on the description and direction I’d hear it louder than anyone. But I don’t. I have no idea what you all are talking about. Don’t get me wrong, I have no doubt there’s SOMETHING, but I’ve NEVER heard it.’ ~ said datamuse
‘Now I can’t sleep because I keep wondering if I’m going to hear this annoying & unusual sound tonight! I think I’ve heard it once before…’ ~ said EJ
…and so on.
Now, I don’t doubt that some people are hearing something. And we have Julie Schickling’s recording to prove that there IS some kind of weird noise that can be heard from the Highland Park area, at least.
So, my favoured explanation for the West Seattle Hum goes like this:
The area of West Seattle and surrounds provides an excellent habitat for the Midshipman fish. Perhaps it has even increased in numbers because of some favourable conditions for breeding, as I have mooted above. It may have even capitulated to evolutionary pressure to increase, by physiological and/or behavioural means, the loudness of its mating call. In the past, people have noticed and mentioned the odd sound – perhaps they were down by the river, perhaps it was a particularly quiet night. It is a very puzzling sound, there is no question. Thus is planted the seed for the idea of The West Seattle Hum. Since a similar sound is heard nearby on Vashon Island, this is a very reasonable starting point for the notion.
The mystery of the eerie sound prompts a level of conversational buzz, which, in the internet age, is quickly amplified (not unlike the hum of the fish itself) until it enters the consciousness of the general population. Now, the West Seattle Hum is a ‘thing’, and all kinds of sounds start getting attributed to it. The idea that it was started from the sounds of a fish is not even known by most people, and since West Seattle is close to numerous industrial centres, mechanical sounds from these places become the more logical focus of attention. This idea is fed by a general distrust of the industry in the precinct – a distrust that is in many cases quite justified (my reading tells me that the plants along the Duwamish have somewhat checkered histories when it comes to community safety and environmental responsibility).
Now comes the Labor Day holiday in September 2012. It’s a very mild night after a long stretch of dry weather – unusual for Seattle. The moon is full. People are out and about for the holiday. In the early hours of the morning – let’s say on Saturday at 1am – with the moon full and the night clear, the Midshipman fish, perhaps in greater numbers than they have been in the past, start their song. It’s very weird, and for whatever reason (perhaps via the stormwater resonance idea I put forward above) the sound carries up into the streets. Quite a few people hear it. However, some people hear other things. ALL these sounds coalesce into one huge, vague phenomenon, with as many disagreements about the source of the sound as there are people recounting their experiences of it.
And then, when some scrutiny comes to bear on the idea – when some video proof that it’s the cement plant would be useful, for example, or some hydrophone recordings of the Midshipman fish could be helpful – there is a mysterious silence. The West Seattle Hum has disappeared once more into the background of normal life.
To sum up: The West Seattle Hum is the workings at the Lafarge plant. It is helicopters. It is the next door neighbour’s airconditioner. It is your imagination. And, it is the fish. If I have to lay my cards on the table, I think it is mostly the fish.