If you’re one of 11% of people who can hear this sound, you may commit suicide!

It's known as the Hum, a steady, droning sound that's heard in places as disparate as Taos, N.M.; Bristol, England; and Largs, Scotland.

But what causes the Hum, and why it only affects a small percentage of the population in certain areas, remains a mystery, despite a number of scientific investigations.

Reports started trickling in during the 1950s from people who had never heard anything unusual before; suddenly, they were bedeviled by an annoying, low-frequency humming, throbbing or rumbling sound.

The cases seem to have several factors in common: Generally, the Hum is only heard indoors, and it's louder at night than during the day.

It's also more common in rural or suburban environments; reports of a hum are rare in urban areas, probably because of the steady background noise in crowded cities.