Expression Media Group

Information and advice

We offer advice and information on any aspect of hearing assistance systems and are happy to talk through any aspect of your requirements or look over plans and specifications, or even carry out on-site surveys to determine the best solution. Call us on 01457 899100 to dicuss your project. Below are listed some of the most frequently asked questions regarding induction loops:

What is an induction loop system?

How does it work?

Does my organisation have to have one?

What are the alternatives to induction loop?

What does it cost?

What is an induction loop system?

An induction loop system allows an audio signal to be sent directly to a hearing aid. The big advantage is that this allows the sound to be heard by the hearing aid user without all the background noise that may exist within a room.

A couple of examples of this would be:

A church - A hearing aid wearer may be sitting in the middle of the church, surrounded by people who are shuffling about, coughing etc, trying to listen to a person speaking quite a distance away. In its standard mode the hearing aid picks up not only the speakers voice but all other noises around which can result in a confused, cluttered sound. The loop system allows the speakers voice to be picked up by a microphone and transmitted direct to the hearing aid (When the aid is switched to the 'T' or telecoil position). The listener then hears this clean, background-noise-free signal.

A doctors reception counter - A hearing aid wearer wishes to talk to a receptionist but the waiting room may be a noisy place with children playing, people talking and even a TV on or background music playing. They do not wish the receptionist to have to raise their voice as confidential matters may be deing discussed. The loop system allows the receptionists voice to be picked up by a small microphone and converted into a signal the hearing aid can pick up directly via the induction loop. This enables them to hear the receptionist without interference from all the background noise in the room.

Reception counter system

Meeting room System

How does it work?

Most hearing aids nowadays have a switch marked M and T. Some even have M, MT and T. The M (microphone) position is for "normal" listening, that is receiving airborne sound via the microphone built in to the hearing aid. The T (telecoil) position is for receiving the sound via an induction coil which is built in to the hearing aid.

For the induction coil to provide sound, a magnetic field is needed via which the sound is transmitted. This facility in hearing aids was introduced by a number of manufacturers many years ago and was then known as the "telephone" or "telecoil" position on the hearing aid switch. It was intended to make it easier for the hearing aid user to hear over the telephone, by picking up the sound via the magnetic field generated by the diaphragm coil in the receiver of the telephone.

In many locations, telephone handsets now have this required capability. In recent years, however, induction loop systems have begun to be provided in public places such as churches, cinemas and theatres, bank, ticket and information counters and desks. It is even found in the home. In all these cases the T facility is used in to listen inductively, without the interference of airborne background sound. The MT position which is provided on some hearing aids allows listening simultaneously both to airborne sound via the microphone and to inductively transmitted sound via the telecoil.

It is well known that when an alternating current is passed through a wire, a magnetic field is generated around the wire. If a second wire is brought within this magnetic field, a corresponding alternating current is created within the second wire. In technical language, it is said that a current is "induced" in the second wire. Hence the term "induction". This particular magnetic principle is the basis on which electrical motors, electrical generators and transformers operate. An induction loop for hearing aid purposes also operates in the same way. An induction loop system consists of an amplifier and a loop. The amplifier can be connected to a sound source such as a TV or radio, a PA / sound reinforcement system or a dedicated microphone.

The signal is amplified and fed into the loop cable, in the form of a strong alternating current. The loop itself consists of an insulated wire, one turn of which is placed around the perimeter of the room. When the alternating current from the amplifier flows through the loop, a magnetic field is created within the room. If a hearing aid user switches their hearing aid to the T position, the telecoil in the hearing aid picks up the fluctuations in the magnetic field and converts them into alternating currents once more. These are in turn amplified and converted by the hearing aid into sound. The magnetic field within the loop area is strong enough to allow the person with the hearing aid to move around freely within the room and still receive the sound at a good, comfortable listening level. The performance of these systems is specified in agreed international standards.

Audio Inputs 1, either from an existing audio source such as a P.A. system or from dedicated microphone inputs feed an audio signal into an Induction Loop Amplifier 2. The amplifier drives a current into a Loop 3 or series of loops. As the current flows through the cable it creates a Magnetic Field 4 in the required area – careful loop and amplifier design ensures that the vertical component of the field is even and free of dropouts and dead zones wherever the user might be. Inside most Hearing Aids 5, a small coil known as a Telecoil 6 picks up the magnetic field signal, which is amplified into a high quality audio signal delivered directly to the ear of the hearing aid user.

Does my organisation have to have one?

In many countries legislation exists or is coming into force to provide equal access to the hearing impaired. In the UK we have the Disability Discrimination Act (DDA).

In general, legislation tends to demand solutions where it can be shown to be reasonable that equal access can be provided. Since October 2004 there is a requirement for all service and function providers to make reasonable, permanant adjustments to their building in order to accomodate those with disabilities. Induction loops are often the most practical, cheapest and lowest maintenance solution for giving good quality access to the hearing impaired, and is therefore becoming the mostly widely adopted solution around the world.

The above legislation is taken to cover many different areas including but not limited to- Shops, hotels, medical centres, churches, leisure facilities, conference centresetc. Even organisations such as the prison service are having to make these changes to accomodate persons with disabilities.

Related links

Disability Discrimination Act

Equality & Human Rights Commission

Simple legislation

What are the alternatives to induction loop?

There are 2 main alternatives to induction loop systems, each of which has its own advantages and disadvantages.

Infra-red systems
Infra-red systems transmit the signal via infra-red light which is invisible to the human eye. These are commonly used where induction loop systems are not able to provide a satisfactory level of performance.
Whilst induction loop system can be severely affected by metal content infra-red systems have no such limitation. Induction loop systems may also have to compete with 'ambient' magnetic signals in the room which can cause a loop to be unusable due to high levels of background hum.
Another significant advantage of the infra red system is confidentiality. Because the signal travels by light it will not be overheard outside the room in which it is being used. The main disadvantage is that anybody wishing to use the facility must have a specialist receiver which the operator of the venue will provide. Care must be taken that these are returned after use or it can be a costly operation!

RF systems
Radio Frequency systems are the second alternative. These have the advatage of being small and easily portable and can be supplied on multiple frequencies so a number of systems can operate within a room. the main disadvatage is the same as the infra-red system in that a special receiver is required for them to operate.

Portable infra-red system

Portable RF based system

What does it cost?

The million dollar question!!!
Well, hopefully not quite that much!

As you can image the prices vary dependant upon your exact requirements. A portable one-to-one induction loop unit supplied mail order is available from less than £100+VAT. Portable RF systems start from less than £300+VAT and portable infra-red kits start from less than £700+VAT.

Installed systems however are harder to give a price for as this will depend upon a whole range of factors including: size of the area to be coverd, building construction, technical complexities, range of inputs etc.
In order to be able to provide you with a guide price please call us on 01457 899100 and we will be happy to chat about your requirements and provide an outline price guide for your project. In some cases we will be able to guarantee this price over the phone, in some we would carry out a free-of-charge site survey to assess all aspects pf the project and then be able to guarantee a price.

You may wish to visit one of our other sites - Expression company site - Sound Advice for Churches - diyAV - Online Store

Please do not hesitate to contact us if you would like any assistance with a project, would like advice or help on a new or existing system, or would like to further discuss our systems, products and services.