Is "The Hum" a mass delusion ?

Sue Taylor first started hearing it at night in 2009. A retired psychiatric nurse, Taylor lives in Roslin, Scotland, a small village seven miles outside of Edinburgh. “A thick, low hum,” is how she described it, something “permeating the entire house,” keeping her awake. At first she thought it was from a nearby factory, or perhaps a generator of some kind. She began spending her evenings looking for the source, listening outside her neighbors’ homes in the early hours of the morning. She couldn’t find anything definitive. She had her hearing checked and was told it was perfect, but the noise persisted. She became dizzy and nauseous, overcome, she says, by a crushing sense of despair and hopelessness at her inability to locate or escape the sound. When things got bad, it felt to Taylor like the bed—and the whole house—was vibrating. Like her head was going to explode. Her husband, who had tinnitus, didn’t hear a thing. “People looked at me like I was mad,” she said.
 Lori Steinborn lives in Tavares, Florida, outside of Orlando, and in 2006 she had started hearing a noise similar to the one Taylor was hearing. Steinborn thought it was her neighbors at first: some nearby stereo blasting, the bass coming through the walls. It would start most nights between 7 and 8 p.m. and last until the early hours of the morning. Like Taylor, she began searching for the sound; leaving town helped her get away from it, but it was waiting when she returned...
The experience described by Steinborn and Taylor, and many others, is what’s come to be known as “the Hum,” a mysterious auditory phenomenon that, by some estimates, 2 percent of the population can hear...
After it was first reported in Bristol, it emerged in Taos, New Mexico; Kokomo, Indiana; Largs, Scotland. A small city newspaper would publish a report of a local person suffering from an unidentified noise, followed by a torrent of letters to the editor with similar complaints...
Hum sufferers have been consistently written off as either delusional or simply suffering from tinnitus...
Further confusing matters is the fact that some reports of the Hum have been definitively traced to specific sources and corrected. The Hum was heard in Sausalito, California, in the mid-1980s, but was eventually found to be the result of the mating sounds of a fish called the plainfin midshipman, whose call could penetrate the steel hulls of the houseboats in the marina. The Windsor Hum was investigated by the Canadian government and ultimately traced to factories on Zug Island, across the Detroit River in Michigan. After an extensive study of the Hum in Kokomo, Indiana, researchers determined that it was caused by two nearby manufacturing plants whose production facilities were emitting specific low frequencies...
Crucially, Deming was able to distinguish the Hum from tinnitus. Tinnitus, usually a ringing in the ear, can take a number of forms, but while its intensity may wax and wane, it is more or less omnipresent, and those who suffer from it tend to hear it in any environment. The Hum, which is constant but only under certain circumstances (indoors, rural areas, etc.), defies a simple correlation with tinnitus. Additionally, Deming notes that if the Hum were related to tinnitus, one would expect a fairly normal geographic distribution rather than clusters in small towns. For a long read on the subject, see the source article at The New Republic.  The embedded image is a screencap from the World Hum Map (zoomable at the source).