Audio induction loop

An induction loop, also induction loop system, induction loop, rare induction loop is a technical device which allows a hearing aid user, trouble- free to receive audio signals such as music or verbal contributions in conference rooms wirelessly through the hearing aid.

Design and operation

The system consists of a signal source (eg, a microphone), an electronic amplifier circuit acting as a transmit antenna and an induction loop to the hearing aid as a receiving device.

The induction loop is in principle a single-core electrical cable which is to be supplied to the space around, for example in the region of the inner walls, installed and connected to the amplifier device. In operation, an electromagnetic field is generated by this cable loop that generates the induction coil of the hearing device by electromagnetic induction an electrical current which is modulated in the same manner as the original audio signal. In the hearing aid that is amplified by the audio amplifier and passed through the transducer to the ear of the wearer.

To provide such induction loop systems use the hearing aid via an induction coil, called the telecoil must (in short: "T- coil ") have who receives the alternating electromagnetic field of the induction loop. Usually, when using the telecoil hearing aid 's microphone is deactivated.

Application

Inductive loop systems are mainly used in public buildings and meeting spaces, such as churches, cinemas, theaters and lecture halls application. Equipped with an inductive pick-up coil locations are reported mostly in the entrance area on a sign in the form of a blue or yellow square with a stylized ear and the letter " T".

For cost reasons or for lack of a large number of users only defined areas with a ring loop are often provided. This is about only certain space groups in cinemas or in a church, which are then marked accordingly. Instead of a fixed installation are also mobile units with the same active principle use.

Benefits

• In general, the signal -to-noise ratio is improved by the use of an inductive sound reproduction system because the audio signal is transmitted directly via the induction loop and noise are hidden.
• Many lecture halls (especially churches ) have a room acoustics, which negatively affects the intelligibility of speech by reverberation or echo, which affects reinforced with impaired hearing. Since the fed into the induction loop signal with a microphone is picked up directly at the sound source, such disturbing effects can be effectively damped.
• Disturbing noises which are generated near the hearing aid wearer can also be hidden by the inductive transfer. However, this applies only if the internal microphone of the hearing aid can be turned off when using the telecoil, which is possible in many devices.

Disadvantages

• A disadvantage can be the use of an induction system environment of high electromagnetic interference ( such as fluorescent lamps, cathode ray tube monitors and mobile devices) impact.
• Since the electromagnetic audio signal normally is not encrypted or encoded, it is possible in principle listen to the broadcast information without authorization and outside of the room with simple means.