Mystery noise bothers residents of Oregon town

For a week, a mysterious high-pitched tone has been interrupting the sleep of people in Forest Grove, a suburb of Portland. The sound has been coming and going for decades.

Here's what it sounds like. It's loud and annoying:

Mystery sound frustrates people in a west Forest Grove neighborhood. Where it could be coming from? #LiveOnK2 @ 11pm pic.twitter.com/p0inj5TBr2

— Chris Liedle (@chrisliedle) February 16, 2016

The tone was unusual for its combination of high pitch and ambiguous point of origin, said audio engineer Tobin Cooley. Higher frequencies like this tone are very directional sounds, versus low-frequency sounds which can seem to come from anywhere or everywhere at once, Cooley said, cautioning that he had listened only to poor-quality recordings but not made a thorough investigation.

What surprises me is that neighbours have not been able to locate where this is coming from.

Cooley speculated that the sound could be coming from a release of compressed air or natural gas, but officials with the local gas company said they had ruled out any of the utilitys equipment or pipelines as a source.

Guardian: Mystery high-pitched noise keeps Oregon town awake at night