n. The confusion experienced by a group of people when a cell phone rings and no one is sure whose phone it is; mistaking a faint sound for the ringing of one's cell phone.
With Britain stuffed full of more mobile phones than people, connected members of the public are developing an increasing number of ways to fret about their handsets.

The result, say experts, is the telecommunications equivalent of phantom limb syndrome, where amputees still feel the sensations of a limb that isn't there any more.

Many of us will be familiar with the basest form of ringxiety — when one phone rings and everyone in the vicinity suddenly starts checking their pockets or handbags with frantic abandon. But some cases become far more complex: individuals have reported hearing their phone ring at concerts, or while driving.
—Bobbie Johnson, “Do you suffer from Ringxiety?,” The Guardian, June 01, 2006
Others say they thought they heard phones ring while taking a shower, using a blow-dryer or watching commercials. What they are hearing is a barely discernable sound — perhaps chimes, a faint trill or an electronic bleat — that they mistake for the ringtone of their cellphone, which isn't ringing. This audio illusion — called phantom phone rings or, more whimsically, ringxiety or fauxcellarm — has emerged recently as an Internet discussion topic and has become a new reason for people to either bemoan the techno-saturation of modern life or question their sanity.

Some sound experts believe that because cellphones have become a fifth limb for many, people now live in a constant state of phone vigilance, and hearing sounds that seem like a telephone's ring can send an expectant brain into action.
—“Brenda Goodman, "I Hear Ringing and There's No One There. I Wonder Why,” The New York Times, May 04, 2006
2004 (earliest)
The second fugitive sought in March was "a term that describes the momentary confusion experienced by everyone in the vicinity when a cell phone rings and no one is sure if it is his/hers." Paul Holman, of Austin, Texas, suggested conphonesion; Pam Blanco, of Warwick, Rhode Island, phonundrum; Alan Tobey, of Berkeley, California, ringchronicity; Jim Hutt, of Blue Mountain Lake, New York, ringmarole; William A. Browne Jr., of Indianapolis, ringxiety; and Gordon Wilkinson, of Mill Bay, British Columbia, fauxcellarm.
—Barbara Wallraff, “Word Fugitives,” The Atlantic Monthly, July 01, 2004