I am only marginally familiar with the concept of sound waves, and/or other forms of energy, being emmitted by movements in the earths crust. I am familiar with caves and cave sciences, having studied and explored hundreds of caves in KY, OH, WV, PA, MD, VA, IN, TN over the past 20 years. And I am at least somewhat knowledgeable about energy transmission in its various forms as I am an engineer. It would seem to me that a void in the earth would somehow change, or modulate said energy waves in some form. So I have two questions for the group:
1. Have the people who claim to hear tones looked into what type of cave systems might lie beneath them?
2. Would not the energy waves produce some type of phenomenom in the cave itself which might be perceptable to a human?

I look forward to your ideas

Get muddy

George