Induction Loop Systems
What is an Induction Loop system?
An Audio Frequency Induction Loop Systems (A.F.I.L.S) is used by hearing aid wearer to assist them to hear clearly in difficult acoustic environments.
How do Induction Loop systems work?
Induction loops replace the sound path between the signal sound and the hearing aid wearer with a magnetic field. The magnetic field is induced into the ‘telecoil’ (hence the ‘T’ programme) which is featured on most hearing aids and converted back to audio. When a hearing aid is switched to the ‘T’ programme the microphone on the hearing aid is (normally) disconnected, so the user simply hears what is fed into the induction loop system, without the background noise.
An induction loop system comprises an input source e.g. microphone, output from sound system, etc, a dedicated loop driver amplifier and an antenna. Systems are available in 3 main types. Perimeter, Low spill phased array and Localised field systems.
Perimeter induction loop systems are the most common and are used in applications where an entire room is to be covered by the loop system. This system has the loop cable run around the perimeter of the room forming a complete ‘loop’, so the whole room is covered by the magnetic field. This would normally be used in churches, village halls, etc. It must be noted that the magnetic field produced by a perimeter loop can radiate for many metres outside the looped area. This is called overspill. Therefore, if confidentiality is an issue or adjacent rooms need systems a low spill over loop should be installed.
Low spill phased array induction loops are used where it would not be possible to cover a room with a perimeter loop. This could be due to the room size or shape, the room having too much metal in its construction (which would affect the performance and frequency response of the loop) or where the magnetic field overspill must be greatly reduced outside the installed room.
Low spill phased array induction loop systems have two amplifiers (although often built into a single unit) that each feed a separate induction loop antenna that is installed to a specific design across the floor (or occasionally ceiling) of the room.
Localised field induction loop systems are used in reception desks, ticket counters, etc. The loop amplifier is fed into a loop coil (usually fitted into the desk) and covers an area of about 1 metre. These systems are available in installed and portable formats.
Example of a localised field induction loop system in a cashiers desk
The hearing aid wearer approaches the counter and tries to communicate with the assistant. As well as picking up the assistant’s voice, the hearing aid’s microphone amplifies all the sounds in the area - the road noise every time the door opens, other customers talking, background music, etc. With this mixture of sounds it can be incredibly frustrating for hearing aid wearers and sometime impossible to hear.
The hearing aid wearer simply switches their hearing aid to the ‘T’ programme and the background noise is significantly reduced. They are now able to hear the assistant’s voice clearly. The signal radiates for approximately 1m from the installed position reducing the risk of other customers hearing the conversation and interference from the positions either side.
In the UK, the installation of induction loop systems is governed by BS7594 (The Code of Practice for Audio-Frequency Induction Loop Systems) and EN60118-4 (Magnetic field strength in audio frequency induction loop systems for hearing aid purposes).
We installed our first induction loop system in 1985 and have now provided over a thousand systems throughout the U.K and abroad. We are approved hearing loop assessors with ISCVE (Institute of Sound, Communications & Visual Engineers).
We also supply and install Speech transfer sound systems with induction loops which includes a loudspeaker and microphone each side of a glazed counter for low level amplification, allowing everybody to hear more clearly.
We can design, supply, install and service any induction loop system. We have installed systems in schools, colleges, universities, village halls, community centres, doctor surgeries, hospitals, churches, chapels, cathedrals, ticket counters, reception desks, theatres, museums, libraries, meeting rooms, boardrooms, council chambers, conference centres and many other premises.
We supply induction loop amplifiers and equipment from all the major manufacturers so can select the most suitable and cost-effective equipment for each customer’s individual needs. For more information please contact us.
Alternative systems are infrared (IR), FM radio (RF), Audio of WiFi and soon to be launched, Auracast (Bluetooth).