Homing In On The Hum
In 1977 the English Sunday Mirror ran a story about someone who claimed to hear a steady and very annoying humming noise. To everyone's surprise, the article elicited some 800 letters from others who heard hums. Amazed by the magnitude of the problem, doctors began examining some of the afflicted. In a few cases, the hum seemed to be internally generated -- something akin to tinnitus, which causes one to hear a highpitched whine. Many others, however, heard a 40 Hz hum modulated at 1.6 kHz, and apparently of external origin. The hum sufferers were inclined to blame industrial noise, but no obvious sources could be uncovered. The hum investigators have considered sea noise, jetstream noise, and other natural sources. Whatever the source, most people do not hear it at all. It is possible that a small percentage of the population is abnormally sensitive to sound at 40 Hz.
(Wilson, Steve; "Mystery of People Who Hear the Hum," New Scientist, 84:868, 1979.)
Comment. Anomalous natural hums are not unknown; viz., the Yellowstone Lake Whispers and "desert sounds." Al-so a select few seem to be able to hear the very low auroras. For more on hums, see GSH5 and GSH6 in: Earthquakes, Tides, Anomalous Sounds. This Catalog is described here.