Acoustic waves travel 5 times faster in water than in air

That is almost 1,500 meters per second, while in air it is only 343. Water molecules are much more densely packed, which allows wave energy to be transmitted more efficiently. In the oceans, there is even a special zone—the so-called SOFAR channel—in which temperature and pressure allow sound to travel hundreds of kilometers. No wonder whale songs can be heard across entire ocean basins. And yet what is a powerful megaphone for a whale turns out, for humans, to be a quiet and slightly unreal world.

The human ear was created to receive waves in air

As the authors of the article What Do You Hear Underwater? in Scientific American point out, the explanation lies in our bodies: when the ear canal fills with water, the eardrum loses its effectiveness. As a result, sound reaches the brain primarily through the bones of the skull and soft tissues—paths we normally use only to a limited extent. This bone conduction is less sensitive and less selective than air conduction, so we hear less and worse. In addition, our natural “acoustic compass” disappears: in water, the difference in the time it takes a wave to reach one ear and the other is five times shorter, and the brain cannot interpret it. A diver hears that something is happening, but has no idea where the sound is coming from—like all sounds surrounding them from every side.

Trying to talk underwater

In air, our voice resonates in the empty spaces of the mouth, throat, and nose, giving it its characteristic tone. Underwater, resonance disappears because vibrations pass from the larynx directly into the tissues and from there into the water. As a result, the sound becomes muffled and stripped of higher tones, sounding as if we were speaking with our mouths closed through a wall. Researchers at Texas A&M University vividly write that underwater our voice is no longer filtered by air—it is the voice of “meat and bone”.

An encounter with silence

This is how divers describe their first impressions. One of them recalled in an interview for the magazine Diver: “I descended a few meters and stopped on the bottom of the pool. Suddenly I realized that I could hear nothing but my own breathing. Then a colleague clapped his hands a few meters away. Instead of a normal clap, I heard something like a strike against a metal plate. But I didn’t know from which side it came!”. This lack of direction and the unfamiliarity of the sound are among the reasons diving can cut you off so strongly from everyday life.

The world beneath the surface is not silent

At the same time, it is worth remembering that underwater we are accompanied by an extremely rich acoustic landscape. It is described, among others, by Amorina Kingdon in the book Sing Like Fish (2024), who points to the concerts of marine life: the crackling of pistol shrimp, the calls of fish, and the melodious songs of whales. For these creatures, hearing is the most important sense—in dark, murky water, sound is often the only way to communicate and orient oneself. Unfortunately, this natural concert is increasingly drowned out by human-generated noise: ship engines, sonar, drilling operations. Physics makes sound in water faster and stronger, but our senses are built to work in air. That is why underwater we hear dull, directionless noises, and our own voice sounds foreign. 

• Amorina Kingdon (2024). Sing Like Fish. Greystone Books.

• Scientific American. (2019). What Do You Hear Underwater?

• Underwater Acoustics for Everyone. (2015).Acoustics Today, 11(3), 24–34.

• West Texas A&M University. (2013). How does sound traveling slower in water make it hard to talk to someone underwater?