Call it the “Earth hum” or even “Earthsong” that you can’t hear without a very sensitive seismometer. The hum’s frequency is near 10 millihertz, below the range of human hearing. (Young humans can typically hear in the range of 15 Hz to 20 kHz; middle-aged humans typically hear in a range of 20 Hz to perhaps 14 kHz).

Researchers in 1998² suggested the “Earth hum” they discovered was being generated in the atmosphere. Subsequent research⁶ pinpointed the sound as occurring along coastlines. The latest research¹ indicates that the hum is generated at coastlines by the slapping of waves and tides on the shallow ocean floor.

Two waves of the same frequency that travel in opposite directions generate a sort of thump-thump-thump sound at twice the frequency of the original waves. The thumping is what people call a “hum.”

The best place to “hear” the hum, according to research, is

near the Vancouver coastline, off Canada, where the shelf is shallow and the ocean waves can be enormous.⁷

This is not the famous “hum” heard in certain locations (such as Bristol, England; and Taos, New Mexico), which is not easily detected by instruments (or all humans, for that matter).

Reference

1. Sharon Kedar and Frank H. Webb
   OCEAN SCIENCE: Enhanced: The Ocean’s Seismic Hum
   Science, Feb 2005; 307: 682 - 683.
2. Kiwamu Nishida, Naoki Kobayashi, and Yoshio Fukao
   Resonant Oscillations Between the Solid Earth and the Atmosphere
   Science, Mar 2000; 287: 2244.
3. W. R. PELTIER
   Global Sea Level and Earth Rotation
   Science, May 1988; 240: 895 - 901.
4. Richard A. Kerr
   AMERICAN GEOPHYSICAL UNION MEETING:
   New Data Hint at Why Earth Hums and Mountains Rise
   Science, Jan 1999; 283: 320.
5. Richard A. Kerr
   High-Tech Fingers on Earth’s Erratic Pulse
   Science, Mar 2003; 299: 2016.
6. Robert Irion
   Tuning In the Planet’s Hum
   ScienceNOW, Sep 2004; 2004: 1.
7. Catherine Brahic
   Earth’s hum linked to coastal waves
   NewScientist.com news service
   17:28 15 February 2007