Have you ever tried to hear underwater? It’s not easy. Rarely can you make out what the other person is saying, let alone which direction the sound is coming from!
Let’s talk about the differences in hearing. When you’re underwater, things change quite a bit. Sound travels in waves. It goes through the air to the ossicle bones in your inner ear. Three auditory bones vibrate and send signals to the brain to decipher the language. Underwater sounds travel 4.3 times faster than on land. We can still pick up sound, but noise often comes out distorted. In all bodies of water, the sound goes straight to the mastoid bone of the skull behind your ear lobes. Essentially, you are using your skull as an ear!
Sound can travel through any state: solid, liquid or gas. However, it travels the same way through each one. The sound is either loud or soft. This is based on amplitude, which is the size of the airwaves and can be adjusted. It can be compared to a volume dial.
Higher amplitude is picked up by the skull. Sadly, humans are unable to hear and decipher lower frequencies. Those sound waves require small ossicles bones. Our ears were developed from the same ancestors as dolphins and whales!
“Whales and dolphins had land-based ancestors that made their way into the ocean millions of years ago. Part of that transition involved modifying their eras, so they could hear sounds underwater and where they were coming from,” says Nick Pyenson, curator of fossil mammals at Smithsonian’s National Museum of History in Washington, D.C.
Your skull acts as a microphone because our body is made up of 65% water. Sound waves cannot tell the difference between your body and the water around you. So the waves travel until they hit something else to vibrate like your skull. The mastoid bone bypasses the ear canal to signal the brain. This is why you can’t tell which direction sound is coming from. The brain activates both ears at once.
In 2011, U.S. Navy researchers determined that humans can hear sounds underwater up to 200,000 Hz. This is 10 times higher than we can hear on land. The natural form of audio reception through bone conduction had led to the invention of several hearing aids. In particular, ones that use the mastoid bone to bypass damaged ossicles or drums were made!