I was visiting relatives in Philadelphia and decided to rollerblade up a bicycle path along the Schulkill River all the way to the edge of Valley Forge park. A couple miles of the path were directly beneath major high-tension electrical wires (by coincidence). I would expect fluctating magnetic fields, although I don't roller blade with a magnetometer. No ear tones. But, a mile or so from my sisters are a series of major radio transmission towers. People who live close sometimes pick up channels on their posters or their braces. Maybe radio waves would be looking at. Maybe the exact size and shape of your skull has to do with what frequency you hear. Maybe, since people around me never ever hear eartones at the same time, someone could check out whether identical twins in the same location can hear them at the same time...
Hey...I'm at least half serious here..

Hey...I was flying out there....23 miles roller blading...twice as far as my previous farthest...and could be the farthest I've done any kind of skating since a skated 200 km on canals in 1 day in northern Netherlands in 1986...the day before over 16,000 Dutch did the same thing in the Elfstendentocht.
Chris