What is a hearing loop and how does it work?

A hearing loop sends a venue's sound straight into the hearing aids and cochlear implant processors of the people listening, with no receiver to hand out and nothing to pair. The idea is simple. The design work lies in making the field strong, even and clear across a real room.

Key points

• A loop is a cable laid around or across the listening area. The audio flows through it as a current and creates a magnetic field that follows the sound.
• A telecoil, a small coil inside many hearing aids and cochlear implant processors, picks up that field and turns it back into sound.
• A loop system has four parts: the audio source, the loop driver, the feeder cable and the loop.
• Listeners hear the microphone signal rather than the room, so distance, echo and noise matter far less.
• Loops suit seated rooms, counters and other defined listening areas. Wide rooms, structural steel, neighboring looped rooms and magnetic hum need more planning.

How a loop reaches the listener

A current in a wire creates a magnetic field around it. In a hearing loop that current is the program audio, so the field rises and falls with speech and music.

A telecoil is a tiny coil of wire inside the hearing device. The changing field induces a small voltage in it, which the hearing aid or processor uses as its input, shaped for the listener's own hearing loss. Telecoils were first added to hearing aids for telephone use, hence the name. The Hearing Loss Association of America estimates that about 70% of hearing aids have one.

To listen, the user picks the telecoil program, often labeled T, or a microphone-and-telecoil program (often MT) that keeps some room sound so they can still hear the person beside them. Some devices switch by themselves when they sense a loop; others need a button or a phone app. In many devices an audiologist has to turn the telecoil program on first.

Telecoils are generally set up to pick up the vertical part of the field, which is what a loop in the floor or ceiling produces over the seats. Loops are designed and measured at head height: usually 1.2 m seated and 1.7 m standing (see listening height).

The four parts of a loop system

What a good loop delivers

IEC 60118-4 is the international standard for these systems. In our own words, its main targets are:

• Field strength: a reference level of 400 mA/m (milliamps per meter) at the listening height.
• Even coverage: across the listening area, the field stays within ±3 dB of that reference.
• Frequency response: from 100 Hz to 5 kHz, the field stays within ±3 dB of its 1 kHz level, so consonants come through as clearly as vowels.
• Low background noise: magnetic noise already in the room is low enough that listeners do not hear it as hum.

Field strength is usually written in dB re 400 mA/m, where 0 dB is the reference. IEC 60118-4 field strength: 400 mA/m and ±3 dB explained covers the targets in depth.

What listeners hear, and why it cuts noise and echo

In a hall, loudspeaker sound reaches each listener mixed with reflections and room noise, and a hearing aid microphone picks up all of it. In the telecoil program, the device receives the venue's microphone signal directly, at a level that changes little from seat to seat. Echo, ventilation noise and crowd rustle drop away, which for many people is the difference between hearing speech and understanding it.

The flip side: a loop carries whatever the feed contains. A poor mix, a muted microphone or hum on the feed reaches the listener too, so good loop work starts at the mixer.

Where loops work best

Loops fit wherever people sit or stand in a defined area to listen:

• worship spaces, such as a 300-seat sanctuary
• council chambers, boardrooms and courtrooms (with overspill planned for)
• lecture halls, classrooms and theaters
• service counters, ticket windows and reception desks, with small counter loops

Nothing has to be handed out or collected, the listener's own device does the work, and nobody can tell who is listening. Signs with the hearing loop symbol, an ear with a T, tell visitors the loop is there.

Where loops need more planning

• Wide rooms. A perimeter loop is strongest a short way inside the wire and weakest in the middle. In wide rooms that difference outgrows the ±3 dB window; phased arrays keep the field even (see phased array hearing loops).
• Steel in the structure. Rebar, steel decks and beams absorb part of the field, most of all at high frequencies (see metal loss).
• Neighboring rooms and private spaces. The field carries through walls and floors, which matters next to other looped rooms or where conversations are confidential (see overspill).
• Magnetic background noise. Transformers, electrical rooms, dimmers and some equipment cause hum in the telecoil program. Check for it on the site survey, because a loop cannot remove it.
• Tiers, stages and balconies. Listeners at different heights need the field planned at each height.

This is where a model earns its keep. In Hearing Loop Designer you set the room, the loop layout and the listening height, and the field is shown in dB re 400 mA/m with the ±3 dB band marked, so a sagging perimeter loop shows up before any cable goes down. Installed performance is confirmed by commissioning. The step-by-step design method covers the whole job.

Common questions

Do listeners need to carry or borrow anything?

Not if their hearing aid or cochlear implant processor has a telecoil: they switch to the telecoil program and listen. People without one can borrow a portable loop receiver with headphones, so venues should keep a few at the front desk.

Do hearing loops work with cochlear implants?

Yes, when the processor has a telecoil and it is turned on, by the audiologist or in the processor's settings. A loop works the same way with hearing devices from different makers, because the telecoil responds to the magnetic field itself; there is no pairing.

Can people outside the room pick up the loop?

Anyone with a telecoil close enough may, because the field carries through walls and floors. Where that matters, the layout is chosen to limit it, for example with a phased array or a cancellation loop, and the result is measured on site. See hearing loop overspill.

How is a hearing loop different from FM, infrared or Auracast?

With FM and infrared, listeners collect a receiver and wear headphones or a neckloop. Auracast broadcast audio reaches compatible hearing devices, phones and earbuds over Bluetooth LE Audio. A loop uses the telecoil already in many hearing devices, and many venues pair it with another system to reach more people. See hearing loop vs FM, infrared and Auracast.

How do you know an installed loop works?

By commissioning it. With a field-strength meter at listening height, the installer sets up the driver, measures background noise, field strength across the listening area and frequency response, and records the results for the venue. A listening walk helps but does not replace measurements. See commissioning a hearing loop.