What is an audio-frequency induction loop system?

Audio-frequency induction loop systems allow hearing impaired people to hear more clearly.

Most hearing aids have a ‘T’ or ‘MT’ switch which allows them to pick up the electromagnetic field generated by an induction loop system. The hearing aid converts this signal into a sound suited to its user’s specific hearing requirements.

Any person with a hearing aid positioned within or near the loop can hear the loop signal by switching their hearing aid to the correct position, allowing them to participate more effectively in general conversation, ordering goods or services, listening to public performances, etc.

An induction loop system therefore comprises the following main elements:-

·          The audio source - typically a microphone, television or radio (or a combination of these).

·          The induction loop amplifier

·          The loop - typically a single turn of wire usually run around the perimeter of the room or a special counter loop fixed to the underside of a table.

·          The receiver(s) - any hearing aid with a ‘T’ or ‘MT’ switch or a specially designed loop listening device.

In addition to the many routine benefits for hearing aid users, induction loop systems can also be used for other limited area broadcasting applications such as museum ‘walk through’ guided tours and surveillance talkback systems.

How does an induction loop system work?

Audio-frequency induction loop systems do not use radio frequencies; they operate at audio frequencies.

The signal from an audio source is fed into an induction loop amplifier, which amplifies and sets the signal level in the same way as a conventional amplifier. The amplified signal, instead of going to a loudspeaker, is fed to a closed loop of cable that is normally placed around the perimeter of the room. Employing a constant current amplifier ensures the current is maintained at the set level whilst providing a flat frequency response without the need for equalization circuitry.

The current flowing through the loop generates a magnetic field that radiates in the space around the loop cable (see diagram below). Any lines of magnetic flux that pass through the telecoil in a receiver, such as a hearing aid, will generate a current in the coil that is then converted back to audio and fed into the listener’s ear.

It is important to remember that the magnetic field will ‘bleed’ outside the perimeter of the loop and therefore a loop system cannot be considered confidential.

Why we have induction loop systems

In normal use, hearing aids utilise a microphone for amplifying localised speech. Whilst this is effective for local conversations/quiet environments, it is less effective for listening to speech or music at a distance or in front of a security screen at a ticket counter. This is because the hearing aid’s microphone also picks up any background noise in the room and unwanted speech from other conversations. An induction loop system works by moving the required sound closer to the hearing aid via the hearing aid’s telecoil which is activated by turning it to the ‘T’ or ‘MT’ position.

As telecoils are fitted as standard to most hearing aids (over 90% are said to have the ‘T’ position) induction loop systems can be considered cost-effective compared to other hearing assistance systems. Infrared systems, for example, require special receivers, the cost and maintenance of which must be met by the service provider.

Many modern hearing aids do not just amplify all frequencies equally; they are tailored to suit the user’s hearing problem and amplify different bands by different amounts. This gives maximum intelligibility, so the user has the best chance of understanding what is said.

Where are ‘aids to communication’ required?

According to the the Royal National Institute for the Deaf (RNID):-

 • Over 9 million people are deaf or hard of hearing (one in seven of the UK population)

• 2 million of these people have hearing aids

• 1.4 million people use hearing aids regularly

• 3 million people experience significant hearing difficulties

Lobbying by organisations such as the RNID has led to increased awareness of the difficulties faced by the hearing impaired, so much so that numerous Standards, Acts and Schemes now recommend the provision of auxiliary aids such as induction loop systems for the hard of hearing, as summarised below. These summaries refer to the published versions of the documents at the time of going to press. If in doubt, full copies of these documents can be purchased or viewed in their entirety from the organisations and/or websites indicated.

BS 8300 (2002)

British Standard BS 8300 is the code of practice for the design of buildings and their approaches to meet the needs of disabled people. The standard recommends that “a hearing enhancement system, using induction loop, infra-red or radio transmission, should be installed in rooms and spaces used for meetings, lectures, classes, performances, spectator sports or films, and used at service and reception counters where the background noise level is high or where glazed screens are used” (9.3.2). It pinpoints the following areas for consideration: seated waiting areas; ticket sales and information points; fitness suites and exercise studios; churches; crematoria and cemetery chapels, educational, cultural and scientific buildings.

The Disability Discrimination Act (1995)

The aim of the DDA is to stop discrimination against disabled people including the hearing impaired. Under the Act, all UK service providers, i.e.,organisations offering goods, facilities or services to the general public, must make ‘reasonable’ adjustments to ensure they do not unlawfully discriminate against disabled people. Employers must also take measures to ensure that employees are not disadvantaged in the workplace. Examples of ‘reasonable adjustments’ include the provision of auxiliary aids, such as induction loop systems, to enable a hard of hearing person to access goods, facilities or services where it is impossible or unreasonably difficult for them to do so. The DDA was strengthened in 2004 when the Disability Rights Commission’s (DRC) Code of Practice came into effect. The DRC is an independent body, established by Act of Parliament, which supports disabled people in getting their rights under the DDA and gives advice to disabled people, employers and service providers.