Audio Frequency Induction Loop Systems (AFILS) give direct listening at meetings/conferences for the hard of hearing. It is becoming more common that this system is provided for fully monitored emergency use, initialising evacuation warnings.
Single phase and split phase systems produce coverage evenly over the intended area.
Privacy from meetings can be designed into the systems with attention to security and importance of limiting transmission.
Most hearing aids 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. 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. Induction loop systems are provided in public places such as churches, cinemas and theatres, and even in the home, and the T facility is used in such cases 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.
Social, welfare and public health authorities have also become increasingly aware of the need for induction loops in sheltered and residential accommodation. Section M of the UK building Regulations also specifies the need for such systems.
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/VA system or a dedicated microphone. It then amplifies this sound signal and sends it out, in the form of an alternating current, through the loop. The loop itself consists of an insulated wire, one turn of which is placed around the perimeter of the room. When this alternating current from the amplifier flows through the loop, a magnetic field is created within the room. If a hearing aid user switches his 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.
Why an induction loop?
In a noisy environment, or one in which reverberations and echoes are noticeable, we all find it difficult at times to hear and understand what is said. But for a person with impaired hearing, wearing a hearing aid, it can be almost impossible to hear and understand under such conditions.
Sound comes to the user in a pure, undistorted form, not affected by the distance the listener is from the sound source, nor by any interfering background noises in the room.
In the sheltered or residential environment, many TV screens have an audio output, which permits a direct connection to a loop amplifier, so that the hearing aid user can listen, via the magnetic field of the induction loop, without other persons in the vicinity being disturbed by sound from the TV (or radio). Some induction loop amplifiers are also available with facilities for doorbell or telephone ringing signals to be transmitted over the loop in such an environment.
Consultancy
We are able to assist in the design and installation of AFILS, which is a very specialised field.
This is especially true where specialised requirements have to be met, such as theatres with balconies, very irregularly shaped rooms, large buildings such as sports halls, cathedrals, similar size churches and concert halls. Additional problems occur due to the large amounts of steel incorporated in modern structures, which cause significant losses.
