A piercing noise that plagued an Oregon city earlier this year, drawing comparisons to "Satan's teakettle" and hypothesized to be everything from a defective water valve to aliens or a signal for the end of times, stopped as suddenly as it started.
In the silence left behind, it appears the mystery may live on forever.
The sound, akin to a bad one-note violin solo broadcast over a microphone with nonstop feedback, began seemingly out of nowhere in February in Forest Grove. Residents of the Portland suburb reported that the sound would usually occur, inconveniently, after dark and last up to a few minutes, according to The Oregonian.
Initially considered just an annoyance, the sound became something of a local celebrity as the story went national, and determining the origin of the notorious noise quickly became a pastime for residents of the city of about 22,000.
A physics professor at nearby Pacific University, Andrew Dawes, created a crowd-sourced map and encouraged people to drop a pin where they heard the noise and note the date and time in hopes of collecting enough data to conclude where it was coming from.
"Anytime there's something that's not explained, it's interesting to look into it," Dawes told NBC affiliate KGW at the time. "I didn't necessarily want it to be my project. It's more of something that anybody can help work on. So if they're interested in solving the mystery, let's do it."
More than a dozen people reported on the map that they heard the noise in various areas of Forest Grove. "Had to cover ears, sounded similar to car brakes squealing, higher pitch," wrote one contributor.
But the map didn't provide an explanation, and speculation took off.
One reader suggested that the sound might be somehow related to fallout from a January standoff between anti-government protesters and authorities at an Oregon wildlife refuge. He may not have realized that the drama unfolded more than 300 miles south of Forest Grove.
Another reader from New York proposed the sound could be coming from street lamps. "These lights can make strange noises when the bulbs start to go," the reader said.
Jimmy Fallon had a theory too, suggesting that only GOP presidential candidate Donald Trump was capable of producing such an ear-offending pitch. The Oregonian reported, to be fair, that several readers had written in suggesting the sound might be democratic presidential candidate Hillary Clinton's voice blaring from a television.
Then people started calling authorities, not just to report the noise, but to share their own — sometimes not-so-educated — guesses.
"Some of the best theories were the mating Sasquatch, an alien mother ship attempting contact, mating drum fish, and finally the sound of the seven trumpets that biblically indicate the end of time," Forest Grove police Capt. Mike Herb told NBC News. "Those are a few of many theories that were written or phoned in from around the world."
Police said hundreds of guesses and ideas to muffle the noise also deluged phones and email servers at the fire department, public works department, engineering department and City Hall. Herb said the calls were becoming a distraction to authorities, which led police to issue a lighthearted but firm warning.
"While there is some fun with the outrageous theories (we think we have literally heard them all — no really, we have), we [have] also made it clear that we firmly believe there is a logical explanation and that we can't condone what might be a prank," the Forest Grove Police Department said in a statement on Feb. 24.
"While some might find it comical, interesting and mysterious, it is unlawful if it is being done on purpose. If this is the case, the individual caught will face possible repercussions."
Shortly thereafter, the noise apparently came to a screeching halt. The police department didn't receive any more reports about it, Herb said, and the last pin was dropped on Dawes' map on Feb. 27.
Herb said the abrupt cessation led authorities to believe that the ear-splitting sound probably stemmed from a prank.
"But I've never confirmed this," Herb added, allowing for the possibility that it was actually produced by a frisky Mr. and Mrs. Big Foot all along.