For weeks, people in the Portland, Oregon, suburb of Forest Grove have been bothered by a mysterious noise. It sounds like an unusually high-pitched train whistle, or an amateur flute player trying to hold a shrill note for as long as possible. And no one can figure out what it is:
The noise in Forest Grove is so annoying that its police chief said it would violate a city ordinance if someone were causing it on purpose. Portland's KATU asked an audio expert what it might be, but he couldn't shed much light on it except to say that the source is probably close to where people are hearing the noise.
This is just the latest entry in the genre of "mysterious noises that come from nowhere." Mysterious booms in the sky from earthquakes and big waves are common. Stories about mysterious "sky trumpets" heard around the world went viral in 2015, but many of them turned out to be hoaxes.