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With its interior similar to a spiral labyrinth, the shell works as a sounding board, which concentrates and amplifies sounds, producing an effect just like the sound of the sea. This phenomenon, known as reverberation, is the sum of the various echoes generated within the shell. “She is, in fact, capturing residual sounds from the environment, those that are not normally registered because they propagate in all directions; that is, they pass straight through the ear”, says otorhinolaryngologist Perboyre Sampaio, from Hospital das Clínicas in São Paulo. The sound waves reverberate inside the shell, reflecting on its walls like someone talking in a cave. It’s worth remembering that reverberation doesn’t come out of nowhere: if we’re in a closed room, in absolute silence, it won’t do any good to bring the shell to our ear.
Australian Aboriginal children play with sea shells: the noise heard inside is just an amplification of the ambient sound
The spiral structure makes the shell act as a sounding board, amplifying ambient sound.