Could ocean waves be making planet Earth hum?
Earth is constantly humming with an ultra-low-frequency vibration that can be picked up right across the globe which has puzzled seismologists for decades. Growing evidence suggests it's the collective sound of the world's oceans constantly moving.
Scientists first detected Earth's low-frequency hum in the 1960s, but its source remained a mystery. Now, researchers believe the hum is caused by ocean waves originating in the Southern Ocean, whose sound reverberates around the globe. The University of Melbourne's Earthquake Research Group is eager to explore the phenomenon further.
The hum, an ultra-low-frequency vibration, was first noticed in the 1960s, yet its origin puzzled scientists for decades. Seismology Research Centre chief scientist Adam Pascale explained that the scientific community thinks the hum results from ocean swell pressure in the Southern Ocean. This pressure interacts with fluid within the Earth's crust, amplifying it into microseismic signals.
Scientists have previously observed peculiar, persistent vibrations traveling through the planet. In 2023, a mysterious signal resembling a regular pulse appeared, baffling researchers. It turned out to be a landslide in a Greenland fjord that created a massive 200-meter-high wave, which oscillated across the ocean like water in a bathtub.
Low-frequency waves cover vast distances, similar to a whale song. Seismology Research Centre chief scientist Adam Pascale noted that most earthquakes are below human hearing, but speeding up the signal can make it audible. Melbourne scientist Rohan Byrne captured the hum using recordings from 30 seismic stations worldwide and sped them up, inadvertently recording an earthquake's rumble at the same time.
Pascale emphasized that Earth still holds many secrets about its workings. Byrne likened the Earth to an orchestra warming up, with each musician playing their unique frequency. Infrasound, or sounds too low for human ears, can be detected by some animals. Byrne suggested that infrasound may explain unsettling sensations in some houses, such as feeling haunted.
Australia's wide-open spaces, far from cities and traffic, make it an ideal location to detect these signals, Byrne explained. The vastness and tranquility of these environments, similar to those used for radio astronomy, contribute to the clarity with which such signals can be detected. The researchers believe that the hum of ocean waves contributes to the Earth being an elaborate, constantly vibrating instrument, struck and set ringing by the forces acting upon it.
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