Why Do Seashells Sound Like the Sea?

Did you ever find a conch shell when you visited a beach? Have you ever held up a conch shell to your ear and heard the ocean’s waves? It’s a favourite memory for many of us and still brings joy.

But have you ever wondered why you hear the ocean, sometimes even when you’re not near one? Let’s look at why and how this happens.

The shape of the shells

Shells come from the sea and around it but, interestingly, don’t have much to do with the sea when it comes to its sound. You’ll notice that shells which are curved give out a louder, clearer sound than others. This is because hollow and curved shells reflect more sound due to their confined space. Hence, conch shells or shells that are spiral in shape mostly tend to sound like the ocean.

Sound enters the shell through its opening and then bounces around till it comes out into our ear. These sounds incline to be low-frequency sounds, mainly from the background that you can’t even hear or notice. The sound of the ocean’s waves is a similar low-frequency sound; therefore, it’s more likely that we hear them when we put a shell to our ears.

The inside of a nautilus shell. Source: Alamy

The sound of shells

But why is it that we always hear the ocean waves only when we put a shell to our ear? Unfortunately, scientists haven’t figured out the exact reason for this yet, but there is a concrete theory.

Scientists have explored the theory that it may be related to our blood pressure. According to this idea, the sound wave-like sound we hear in the shell is actually the sound of blood flowing through our head and ear, which echoes in the shell. By this logic, if our blood flow increased then the sound from the shell would be louder and faster. When they tested it by exercising to increase heart rate and blood flow, they found that the sound didn’t change at all – it was the same slow, calming oceanic sound.

Another hypothesis was that the sound was caused by the whooshing of air near the ear as the shell was cupped around it. But they tested this theory in a soundproof room, which would still have air, but there was no noise.

The most widely-accepted theory is that the shell picks up any background noise around you when you put it to your ear. It can be any low-frequency sounds we hardly detect like traffic on a nearby road or the hum of the fan or fridge. These sounds bounce around the spiral shell, and since they’re not super distinct, they sound like the waves of the sea.

But you don’t need a shell to test this theory out. Simply use a clean drinking glass and cup it over your ear, you will hear the sea.