Wikipedia
An earmold (ear mold British ear mould or earmould) is a device worn inserted into the ear for sound conduction or ear protection. Earmolds are anatomically shaped and can be produced in different sizes for general use or specially cast from particular ear forms. Some users specify how hard or soft they want their mould to be, an audiologist can also suggest this. As a conductor, it improves sound transmission to eardrums. This is an essential feature to diminish feedback paths in hearing aids and assure better intelligibility in noisy-environment communication. The main goal in wearing earmolds is to attain better user comfort and efficiency. Earmolds (and their tubes) often turn yellow and stiff with age, and thus need replacement on a regular basis. The job of making earmoulds is very time-consuming and skilful; each one is made individually.