Well, it’s only “little” when considering the ultralow frequencies involved. In fact, it’s a massive tune. It’s a world-wide phenomenon and probably as old (thus long) as the Earth itself. The linked article summarizes years of research into a perpetual hum that has been detected in places such as Antarctica, Algeria and on the floor of the Indian Ocean.
The coming decades will clarify the relation between our body and certain facts about the environment on this planet, particularly previously-hidden “features” such as this humming. I’m going to keep my ears on the ground for more news about the Earth’s song. See what I did there?