NewtoJacksonvilleFl wrote:... My husband can hear it, but he wears ear plugs and can block it out.
If he can block it out with ear plugs, then it's not an electromagnetic humm. This humm is not audible; it's internally sensed and perceived due to the harmonic vibration. It can be "heard" most when local sounds are blocked, such as at night in a well insulated room or in a closed-up car without the engine running. The quieter your surroundings, the more your body perceives the harmonics and vibrations. Your brain interprets it as an audible sound, but it is not auditory. It's vibrational.
Think of it this way: A dog can hear higher frequencies that a human cannot. Human beings have a certain auditory frequency range. When we are exposed to those frequencies outside of our audible range, our bodies can sometimes still perceive the vibration of the inaudible sound. That is what the humm is all about. We're not technically hearing it within our aural range. Instead, this lower frequency outside of our audible range is being perceived through harmonic vibration. This electromagnetic harmonic vibration picked up by our bodies fools the auditory cortex of the brain so that we think we "hear" it as if it was in our audible range.