Could the mating call of the Midshipman fish be the culprit?
UPDATE: The West Seattle Hum has been identified as coming from an industrial operation that vacuums dry goods (like wheat) out of ships' holds. Just as everyone suspected, it's not aliens or fish: it's industrial noise.
Last week, several West Seattle residents reported being bothered by a loud droning low-frequency hum that could be heard at night. One resident even managed to catch some great audio of the sound, which you can here archived here on the West Seattle Blog. Her recording starts with some typical street noises, but the hum kicks in around :30.
This hum has been heard off and on throughout the years. I remember hearing it when I lived on Alki, it was something that echoed through the air in the wee hours of the late summer nights, when the city was sleeping. I worked night shift, so I was awake when most people were not. I always wrote it off to the multitude of light and heavy industry sites within a few miles, from cargo containers being loaded at the shipyards, to the steel mill right beside the West Seattle bridge.
But this time, residents complained, and all the businesses in the area claimed it wasn't them. So what, then, could be the cause?
Some people think they have found the answer. But frankly, I have my doubts. Just because you see something on the evening news, that doesn't make it true! Even Jim Forman seems skeptical about this one.
The culprit, so some claim, is the Midshipman fish. This small bottom-dwelling fish produces a very loud mating call. It is a droning hum at about the same frequency range as the West Seattle hum. The Midshipman fish mates in late summer, and at night, which matches the time that the noise is being reported.
(Then again, perhaps you just can't hear it during the day. West Seattle has a lot of ambient noise during the daytime that would mask many subtle noises.)
The raw call of the Midshipman fish is only somewhat similar to the West Seattle Hum. And although it is loud for a fish, even marine biologists doubt that the noise could carry for miles overland to wake West Seattle residents.
However, someone pointed out that last week - when the hum was being reported - an empty container ship was docked at the mouth of the Duwamish. The theory is that the ship served as a resonance chamber for the Midshipman fish's mating calls, booming the noise out to the surrounding area. This would certainly account for the West Seattle Hum's distinctly metallic sound. But to be honest, I still don't buy it. I will be eager to see what new theories and evidence turns up in the nights to come.