Please search if someone already wrote it, like me for example
https://steemit.com/education/@rossenpavlov/why-we-hear-the-ocean-in-seashells
What we hear is the ambient noise around us. The shape of the seashell acts like a resonator and different frequencies are augmented. The size and shape of the seashell determine the actual sound we perceive. Any cone-shaped object can be used to demonstrate this phenomenon, such as an empty cup or by cupping your hands over your ears.