Why Do Shells Sound Like the Ocean?

Ambient noise is amplified by a seashell’s curves, which is what makes it
sound like the ocean.

Shells sound like the ocean because the curved shape of a seashell
amplifies the ambient noise, or background noise, that normally is too
quiet to be heard. This occurs because air bounces within the shell and
makes sound, which varies in pitch depending on the size of the shell. A
small seashell might produce a higher-pitched, more ocean-like sound than
bigger shells because the air bounces around more quickly. Holding a glass
or forming the mouth into an "O" shape and quickly tapping the cheek or
throat will produce the same type of sound effect as the shell because it
causes air to vibrate within a tight space.
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