Seashell resonance refers to a popular

folk myth Folklore is shared by a particular group of people; it encompasses the traditions common to that culture, subculture or group. This includes oral traditions such as tales, legends, proverbs and jokes. They include material culture, ranging ...

that the sound of the ocean may be heard through seashells, particularly

conch Conch () is a common name of a number of different medium-to-large-sized sea snails. Conch shells typically have a high spire and a noticeable siphonal canal (in other words, the shell comes to a noticeable point at both ends). In North Am ...

shells. This effect is similarly observed in any resonant cavity, such as an empty cup or a

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each " ...

clasped to the ear. The resonant sounds are created from

ambient noise Background noise or ambient noise is any sound other than the sound being monitored (primary sound). Background noise is a form of noise pollution or interference. Background noise is an important concept in setting noise levels. Background n ...

in the surrounding environment by the processes of

reverberation Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abs ...

and (acoustic) amplification within the cavity of the shell. The ocean-like quality of seashell resonance is due in part to the similarity between airflow and ocean movement sounds. The association of seashells with the ocean likely plays a further role. ''Blood flow in the ear resonates in the shell causing an sound similar to the sound of waves.'' Resonators attenuate or emphasize some ambient noise frequencies in the environment, including airflow within the resonator and sound originating from the body, such as bloodflow and muscle movement. These sounds are normally discarded by the auditory cortex; however, they become more obvious when louder external sounds are filtered out. This occlusion effect occurs with seashells and other resonators such as circumaural headphones, raising the acoustic impedance to external sounds.

References

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External links

How Stuff Works
Mollusc shells Acoustics