The Earth Is Humming But We Can’t Hear It

The earth hums. Not from industrial noise or human interaction, but on its own. Even though scientists have suspected this for quite a long time (the first paper written about it was in 1959), the hum was only recently recorded by a group of Japanese researchers. The problem is that it’s so low that we can’t year it.

What’s the frequency? There are actually two peaks to the hum – one at at 2.9 millihertz and the other at 4.5 millihertz. This is really down low, as it’s about 10,000 times lower than the human threshold of hearing, which textbooks say is around 20 to 30 hertz. In other words, it’s so low that we can’t hear it, but that doesn’t mean it’s not there.

What creates the hum? Scientists aren’t totally sure yet, but they believe it’s generated by ocean wave motion and seafloor currents, That being said, the Earth expands and contracts very slightly all the time, creating a steady sound that’s also inaudible. No one really knows why this happens, but scientists think that ocean waves could again be the source.

The real problem with recording the hum is the fact that’s there’s so much other earth-related movement going on, like volcanos and earthquakes. These events, coupled with wildlife noises and ship traffic, tend to obscure the hum data that was being tracked, but new filters, noise reduction apps and algorithms provided the window needed to only measure the earth hum and nothing else. Also, the researchers ended up in a relative quiet place in the Indian Ocean near Madagascar, where they deployed seismometers over an area measuring about 772 square miles.

Just to be clear, the Earth also creates another set of noises known as the Shumann Resonances that are the result of Earth’s magnetic field. These resonances occur at  7.83 Hz (which is the fundamental), 14.3, 20.8, 27.3 and 33.8 Hz, but these are distinctly different the hum that these researchers were after.

Why the science lesson today? It’s just another way to show that everything around us is vibrating, and as musicians, engineers, producers and songwriters, we’re allowed to harness a little of that energy to shape it in a different way. Enjoy the ride!