Abstract: Failure of the acoustic seal in “in-the-ear” hearing aid earmolds is a principle cause of acoustic feedback. The ongoing development of smaller hearing aids with close proximity between the hearing aid microphone and receiver mandates the highest quality earmold fit. This invention relates eliminates the feedback problem by placing a soft, pliant, and durable hydrogel coating (16) on the earmold (18) The coating swells after the hearing aid is inserted and, thus, seals off any pathways for acoustic feedback. After removal at night, the earmold dries and returns to its smaller size, ready for insertion the next day.