It is well known that the Hum is much louder indoors than outside so it must be that the energy causing the Hum is greater inside of a building.
Buildings act as conduits,funneling the energy, especially if the building has a pointed roof.
Isolated buildings on high ground also produce a higher Hum level.
The energy flowing through the building is concentrated by collecting energy from the immediate vicinity, hence it is also affected by the type of ground on which the building stands.
There is a rough analogy here with objects in an electric field where the intensity increases at sharp isolated points.
For those people sensitive enough to hear the Hum outdoors, the following simple test can be tried.
Stand in an open field and carefully estimate the Hum level, then lay flat upon the ground and observe the difference. In the standing position the body acts as a conduit allowing an increase in the flow of energy.
During this test a pair of ear protectors should be worn to remove extraneous noise allowing the observer to concentrate on the Hum.
The following is a quote taken from the Investigation into the Taos Hum by the University of New Mexico August 23 1993
The receptor cells of the cochlea in the inner ear are the subject of increasing interest. In the last ten years scientists have learned that they don’t just receive sound but vibrate and can be provoked or tuned to resonate at particular frequencies. Something in the environment may be causing people’s ears to emit sounds they can then hear: End quote.