Earplugs and other ear protection devices have been developed and constructed to protect human (or other animal) ears from damaging effects of loud noises, whether constant or sudden. Present mechanical earplug technology uses a variety of constructions, which may provide benefits in different high noise environments. Some constructions use a sound deadening material, such as foam, to block or lessen sounds entering the ear canal. Other constructions include acoustic filters, such as cavities, side branches, or other apertures for redirecting sound waves, or vibrating diaphragms for absorbing sound waves.
Some earplugs attenuate sounds based on acoustic frequency. This allows for discerning sounds of useful frequencies, such as those used in speech, while blocking sounds of potentially harmful frequencies. This, however, may prevent an individual using the earplug from hearing some useful sounds that may be out of the designated frequency range. Electronic earplugs exist as well for actively attenuating or amplifying sound. Such earplugs use microphones, electronic circuitry, speakers, and a power source, which add to the cost of the earplug and may require some maintenance to ensure operation via power source and/or circuitry.