Mystery screeching sound haunts small US town

A high-pitched mystery noise has been baffling and annoying residents of a small US town for more than a month with experts at a complete loss to explain where the sound is coming from.

Locals in Forest Grove, Oregon say the shrill sound comes at different times of the day and night and sounds like car brakes screeching.

Paula Lynch recorded the sound on her mobile and posted it on Facebook.

She told KGW-TV it was the third time in a week she had heard the strange and annoying noises.

“My first instinct was that it was a gas line issue and there might be an explosion,” Ms Lynch said, adding that she had called police to report the sound.

Local authorities have ruled out the possibility of the noise coming from gas lines, utility relief valves or fire alarms.

The noise also has audio experts like Tobin Colley baffled.

After listening to a recording of the sound, Mr Colley told KATU: “It sounds like some sort of pressurised gas or air through a fitting or valve or something”.

“It's not steady state and you can't predict when it's going to happen. Those are all interesting sound features.”

The sounds must have been coming from nearby as high-pitched tones don't usually travel very far, he added.

In a Facebook post, Forest Grove police department said it had been bombarded with “unsolicited theories and solutions from all over the world”.

“While the source could likely be a prank, this is not confirmed to be the case,” the post read.

“It is unlawful if it is being done on purpose.”