There is a popular folk myth that if one holds a seashell—specifically, most often, a conch shell—to one's ear, one can hear the sound of the ocean.
The rushing sound that one hears is in fact the noise of the surrounding environment, resonating within the cavity of the shell. The same effect can be produced with any resonant cavity, such as an empty cup or even by simply cupping one's hand over one's ear. The similarity of the noise produced by the resonator to that of the oceans is due to the resemblance between ocean movements and airflow.
The resonator is simply attenuating some frequencies of the ambient noise in the environment, including air flowing within the resonator and sound originating within the human body itself, more than others.
The human ear picks up sounds made by the human body as well, including the sounds of blood flowing and muscles acting. These sounds are normally discarded by the brain; however, they become more obvious when louder external sounds are filtered out. This occlusion effect occurs with seashells, cups, or hands held over one's ears, and also with circumaural headphones, whose cups form a seal around the ear, raising the acoustic impedance to external sounds.
"Seashell resonance." Wikipedia
These sounds were produced on 2 eurorack modular systems by Boris Uytterhaegen & Lieven Stockx on Tuesday 7th of May 2016.
