Why do we hear the sound of the sea or the ocean when we plug our ears with shells?

Everyone puts a sea shell when it is lifted from the shores of the seas, automatically to the ear, trying to hear the sound of the seas and oceans, but why can sounds similar to the sea be heard inside the shell?

“It’s not the sound of the sea, but because you’re holding a shell to your ear, people might think it might be noise,” said Trevor Cox, professor of acoustic engineering at the University of Salford in the UK.

“You hear ambient or background noises that are amplified by the physical properties of the shells,” said Andrew King, director of the Oxford University Center for Integrative Neuroscience and chairman of the Oxford Auditory Neurosciences Group.

King explained that the “hard, curved surfaces” inside the shells reflect sound waves, causing the waves to bounce back into the shell. Accordingly, King told Live Science in an attempt to explain what an audible sound is: “The cerebral cortex acts like a resonator, amplifying certain sound frequencies so that they are louder than if the shells were not located near the ear.”

According to King, the frequencies you hear depend on the size and shape of the shells: if the shells are irregularly shaped, they are more likely to resonate at multiple frequencies.

“The shell is like a wind instrument,” Cox said. “It has a resonant frequency range where the air inside the shell vibrates more. Hold the shell up to your ear. It’s these ambient sound frequencies that get amplified, and as the sound changes, your brain pays attention to it.” “.

You don’t actually need a seashell to hear the sound of the ocean, according to Cox and King, you can have a similar experience at home by simply using a cup or bowl.

“The same effect is created if you put other objects or even bend your arm to some extent – next to the ear, what you hear again is determined by the size and shape of the object,” King said. “You won’t hear anything in a completely soundproof room,” King said.

“If I go into an anechoic room at Salford University, which is a completely silent room, I won’t hear anything because there is no ambient sound,” Cox said.

Source: Living Science