An earplug's a device that's meant to be inserted in the ear canal to protect the wearer's hearing from loud noises or the intrusion of water, foreign bodies, dust or excessive wind. Protection from water Some earplugs are primarily designed to keep water out of the ear canal, especially during swimming and watersports. These may be made of wax or moldable silicone which's custom-fitted to the ear canal by the wearer. A 2003 study published in Clinical Otolaryngology found that a cotton ball sat… (More on Earplug)