Written and maintained by CASRAI Editorial Board
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This page describes products and general use; it is not medical advice.
Short answer: a hearing aid telecoil (also written t-coil or “hearing aid t coil”) is a small coil of wire inside a hearing aid that picks up a magnetic signal and turns it back into sound, so the wearer can hear a loop system or a compatible phone without relying on the aid’s microphone. It is used by people who wear hearing aids or cochlear implants that include one, and by the clinic staff who fit, check and stock them.
What a hearing aid telecoil is
The National Institute on Deafness and Other Communication Disorders (NIDCD) describes a telecoil as a small magnetic coil that lets users receive sound through the circuitry of the hearing aid, and also as a coil of wire installed inside many hearing aids and cochlear implants. NIDCD adds that a telecoil helps people hear in public facilities that have installed special sound systems, called induction loop systems.
How a telecoil works
A telecoil does not listen to the room. NIDCD explains that it works by receiving an electromagnetic signal from a hearing loop and turning it back into sound. A hearing loop is a thin loop of wire that encircles a room or branches out beneath carpeting, and loop systems use electromagnetic energy to transmit sound.
An ASHA article (2011) notes that in telecoil mode the hearing aid microphone can be disabled.
Which hearing aids have a telecoil
NIDCD lists the telecoil as an optional feature: some in-the-ear (ITE) aids may have added features installed, and canal aids are less likely to include one because they have less space for batteries and additional devices such as a telecoil. Whether a particular model has one is stated by its manufacturer.
Loops, neckloops and silhouette inductors
A telecoil can receive several kinds of magnetic signal. The table summarizes the signal paths named in the NIDCD and ASHA sources.
| Signal path | What it does | Source |
|---|---|---|
| Hearing loop (room or venue) | A wire loop around a room or under carpeting transmits sound by electromagnetic energy; the telecoil receives it and turns it back into sound. | NIDCD, assistive devices page |
| Neckloop | Worn around the neck; converts an audio signal into a magnetic signal picked up directly by the telecoil. | NIDCD, assistive devices page |
| Silhouette inductor | Worn behind the hearing aid or implant; converts the signal into a magnetic signal picked up by the telecoil. | NIDCD, assistive devices page |
| Phone with a T-rating | The T-rating reflects the strength of electromagnetic induction available to a hearing aid’s telecoil. | ASHA (2011) |
For how a neckloop fits into a personal listening setup, see what an FM system is.
Phone T-ratings explained
ASHA’s 2011 article explains the rating scheme used for wireless phones. Phones carry an M rating (1 to 4) for microphone mode and a T rating (1 to 4) for telecoil mode; the T rating reflects the strength of electromagnetic induction available to a hearing aid’s telecoil. Under ANSI C63.19, a phone is considered hearing-aid compatible if it receives an M and/or T rating of 3, and the article describes those ratings as applying to a hearing aid rated M2 and/or T2. This is a 2011 source, so check the current standard and the phone and aid manufacturers’ documentation for present-day ratings.
Safe use and common mistakes
- Assuming every hearing aid has a telecoil. NIDCD describes it as optional, and canal styles are less likely to include one.
- Treating a telecoil as a microphone feature. It receives a magnetic signal, not room sound.
- Overlooking related supplies. See hearing aid cleaning tools and earmold types for the products that go with hearing aids.
Programming and any individual hearing needs are matters for the wearer’s audiologist and the aid’s instructions for use. Related reading: personal sound amplification products (PSAPs). Clinics building a stock list can start from the audiology clinic supply checklist.
FAQ
What is a hearing aid t coil?
It is the same thing as a telecoil: a coil of wire installed inside many hearing aids and cochlear implants that receives an electromagnetic signal, for example from a hearing loop, and turns it back into sound (NIDCD).
Do canal hearing aids have a telecoil?
They are less likely to. NIDCD notes that canal aids have less space available for batteries and additional devices such as a telecoil.
Can a telecoil work without the aid’s microphone?
Yes. In telecoil mode the hearing aid microphone can be disabled, according to ASHA (2011).
Sources
- NIDCD, Hearing Aids (page updated Oct 11, 2022; checked 2026-10-30).
- NIDCD, Assistive Devices for People with Hearing, Voice, Speech, or Language Disorders (page updated Nov 12, 2019; checked 2026-10-30).
- ASHA, Wireless Device Compatibility (Sept 2011; checked 2026-10-30).
