Earth has a strange hum that people are hearing around the world

Do you sometimes hear an odd noise and can't quite place it? Well you're not alone. Millions of people around the world can hear a slight humming noise.

So what is it?

A 1998 University of Tokyo study found Earth is constantly creating a low-frequency vibration and some people can actually hear it.

Although we can't feel it, scientists believe that it might be caused by the planet contracting. The humming is often heard during certain months and locations around the globe.