Some say it's like a diesel engine idling. Others describe it as a deep drone or fluorescent light-like buzz. And a great many people don't hear anything at all.
Complaints about the "Kokomo Hum" began in 1999, when a handful of local residents began to report a constant low-pitched rumbling noise. They say they developed a range of mysterious health problems soon after, including dizziness, diarrhea, extreme fatigue, joint and muscle pain, nosebleeds, and excruciating, unending headaches.
Just had my radio interview. There were fascinating stories, but it all resembles this, and other mysterious hums. So, most likely it is industrial and not geological. ....too bad. The geology would come into play with the local soil conditions which could amplify it by a factor of 10 to 100. I still think seismometers are a good idea, but we put them on firm ground, and I bet they won't pick up a thing! Most likely, the tuning will get out of phase again, and it will stop.
We once were trying to install a seismometer north of Toronto. The ground was singing, so that the seismometer was useless. It was all over the area, and there were no heavy industries. What was it? Who knows?