Understanding Marine Animal Communication: How Does Sound Travel Underwater?

While we don’t usually think of it this way, the sounds we hear are vibrations in the air. When we speak, our vocal cords are vibrating, producing sound waves. These sounds waves can pass through anything: gasses (like the air we breathe), solids (like the walls of your house), and even liquids (like sea water).

In water, sound actually moves faster than it does in air. Added to that, in the ocean sound waves can become stuck in what scientists call the Sound Fixing and Ranging (SOFAR) channel, 2,000 – 4,000 feet (600-1,200 meters) below the ocean surface. The SOFAR channel is the region of the ocean where temperature and pressure is rapidly changing, which causes sound waves to become trapped, bouncing between these areas of rapidly changing temperature and pressure. Because the sound waves are bouncing around in the SOFAR channel, they are actually able to travel greater distances without losing energy.

The SOFAR channel is a region of the ocean where pressure and temperature change rapidly. These changes in the physical properties of the water result in a region where sound waves become trapped and are able to travel much greater distances. Image courtesy of Sound in the Sea 2001

To learn more about the ocean acoustics and the SOFAR channel, check out the National Oceanic and Atmospheric Administration’s website.

For species like the fin whale, which produce very low frequency calls that travel long distances, scientists believe the SOFAR channel may actually allow individuals to communicate across entire ocean basins.

In practice, for whales to be able to communicate at this range, both the caller and the receiver would need to be in the SOFAR region. Thus it seems more likely that, for the most part, whales probably communicate at the range of hundreds of miles.

Fin whales are the second largest animal, second only to blue whales. These two species also produce the lowest frequency and loudest calls on earth. Image courtesy of NOAA Northeast Fisheries Science Center

Fin whales and blue whales make the lowest frequency sounds of any animal. Check out the Northeast Fishery Science Center’s acoustics program website to listen to these and other calls.