29/08/2026
People research hearing aid brands and features endlessly, but rarely ask about the small piece that actually sits in the ear canal. That piece does more to determine comfort, clarity and whistling than almost anything else.
It is either a dome, a soft silicone tip in standard sizes, or a custom mould made from an impression of your own ear. The choice affects how much sound reaches your eardrum, how much escapes and causes feedback, how your own voice sounds, and whether the aid is comfortable after a full day.
Domes involve a genuine trade-off. An open dome is heavily vented, feels natural and keeps your own voice sounding normal, but lets amplified sound leak out. When that reaches the microphone you get whistling. A closed or power dome seals better and allows more amplification, at the cost of a more plugged sensation.
A custom mould follows your canal exactly, sealing without pressing outwards, with the vent drilled to a precise size. Moulds usually suit moderate or greater losses, awkward canal shapes, persistent feedback, or anyone who finds a small handle easier to insert.
Signs the coupling is wrong: whistling when you hug someone or put a hat on, working loose during the day, your own voice sounding hollow, speech clear at home but lost in company, or soreness by evening. All are adjustable at a review rather than requiring a new hearing aid.
Wax is the main enemy of both. A blocked dome or mould bore is the commonest reason an aid gradually sounds weaker.
Read more in our blog: https://hearwithish.com/hearing-aid-domes-and-custom-moulds-why-the-small-part-in-your-ear-matters-most/