Acoustic science explains the sound heard in seashells

The sound heard when placing a seashell against the ear is not the sound of the ocean, but rather amplified ambient noise. According to Trevor Cox, a professor of acoustic engineering at the University of Salford, the shell acts as a resonator.

Andrew King, director of the Centre for Integrative Neurosciences at the University of Oxford, explains that the hard, curved internal surfaces of the shell reflect sound waves. This causes certain frequencies from the surrounding environment to become more pronounced. The brain then interprets these amplified frequencies as a deep noise similar to ocean waves.

The specific sound produced depends on the size and shape of the shell, as irregular shapes can resonate at multiple frequencies. This effect is not exclusive to seashells; similar acoustic amplification can be achieved using objects like a cup, a bowl, or even a cupped hand.