What is "The Hum"?

Only about 2 percent of the people living in any given Hum-prone area can hear the sound, and most of them are ages 55 to 70, according to a 2003 study by acoustical consultant Geoff Leventhall of Surrey, England.

Most of the people who hear the Hum (sometimes referred to as "hearers" or "hummers") describe the sound as similar to a diesel engine idling nearby. And the Hum has driven virtually every one of them to the point of despair.

"It's a kind of torture; sometimes, you just want to scream," retiree Katie Jacques of Leeds, England, told the BBC. Leeds is one of several places in Great Britain where the Hum has recently appeared.

"It's worst at night," Jacques said. "It's hard to get off to sleep because I hear this throbbing sound in the background … You're tossing and turning, and you get more and more agitated about it."

Being dismissed as crackpots or whiners only exacerbates the distress for these complainants, most of whom have perfectly normal hearing. Sufferers complain of headaches, nausea, dizziness, nosebleeds and sleep disturbances. At least one suicide in the United Kingdom has been blamed on the Hum, the BBC reports.