Sennheiser Infrared Systems

Sound Induction Systems supply, service and install infrared hearing systems throughout the UK.

Infrared system What is an infrared hearing system?

An infrared hearing system is an assistive audio system to aid communication with hearing impaired people and is a popular alternative to an induction loop system. A typical system consists of an audio source, an infrared radiator (transmitter) and infrared listening receivers.

Sennheiser infrared hearing systemHow do infrared hearing systems work?

1 The input to an infrared system can be from a microphone, a sound system or any other audio source. They each produce an electrical signal which contains the audio information.

2 This signal is fed to the modulator which prepares the audio signal for the subsequent infrared (IR) transmission.

3 This processed electrical signal is then fed to the radiator. The radiator diodes produce the (invisible) infrared light and radiate it into the room.

4 Wireless receivers are used to convert the infrared light signal back into an electrical signal and then into an audio signal again (or a personal induction loop if used by a hearing aid wearer). There is no limit to the number of receivers that can be used on a system.

Most infrared hearing systems are single channel and use a radiator with an integrated modulator.

The easiest way to regard infrared radiators is to think of them as floodlights of invisible light. Radiators are available in different sizes depending on the area of coverage and the number of channels required. In most applications multiple radiators are used to ensure an even coverage of the light so the user doesn’t experience blind spots. With the exception of the smallest model, radiators are available in either a black or white finish.

Sennheiser infrared radiator

 Receivers are required to convert the infrared light to audio. They are available in two types-

Neckloop receiver

Sennheiser infrared induction loop receiver           

Neck loop infrared receiver


This lightweight two channel receiver has a 3.5mm jack socket to connect a personal induction loop for use with a hearing aid. The user simply switches their hearing aid to the “T” (telecoil) position to hear the audio signal. Alternatively, the neckloop can be unplugged and headphones can be used for users who do not wear a suitable hearing aid. The bodypack is switched ON/OFF by pressing the button in the centre of the black volume control. Channels are selected by pressing the CHANNEL button on the rear.

Stethoset receiver

Sennheiser infrared stethoset receiver                                     

Infrared stethoset receiver

This lightweight two channel receiver is for use by people who do not wear a hearing aid. The receiver has arms with soft rubber pads which sit on the ears allowing the receiver to hang below the chin. The receiver automatically switches ON when worn and OFF when removed to extend battery life. The user simply selects the channel by pressing the CHANNEL button on the rear and then adjusts the volume using the black ergonomic dial on the front.

NB. Receiver channel selection can be disabled for single channel infrared hearing systems. Please contact us for details.

Both types of receivers use lithium polymer accupack rechargeable batteries which are charged in 10 way racks.

Sennheiser infrared receivers in charging rackWhy use an infrared hearing system in place of an induction loop system?

Infrared hearing system have many advantages over induction loop systems-

-Infrared light cannot penetrate walls or ceilings so overspill does not occur, unlike perimeter induction loop systems. This allows systems to be used in adjacent rooms and in rooms where confidential meeting take place e.g. Court rooms, boardrooms, interview rooms, etc

-There is no loop wire to run around the perimeter so it is easier to install in rooms with multi-levels e.g. Theatres, or wide areas e.g. Exhibition halls.

-As infrared light carries the signal there are no losses due to the amount of steel in the construction of the room which can affect the signal and frequency response of induction loop systems. Systems can also be used (with stethoset receivers) in environments with high background magnetic interference.

-Portable infrared hearing systems (like the SENNSIS systems) are quicker to set up than portable induction loop systems as there is no wire antenna to install around the perimeter of the room. There are also reduced Health and Safety issues associated with trailing wires.

-Multichannel systems are available.

For multichannel infrared systems an external modulator is installed which feeds the radiators. Typical examples where twin channel infrared systems are used are-

-In a cinema, a twin channel infrared system would be used to feed the film soundtrack for hearing impaired people on one channel, and an audio description to assist visually impaired people on the other channel. Signs and an announcement before each film inform customers that the system is available. Receivers are then issued to the customers who request to use the system.

-In a council chamber or conference room where bilingual meetings take place and a hearing support system is required (to comply with the Disability Discrimination Act). In this case one channel of the system would be fed by an interpreter’s microphone, and the another channel fed from the floor language via microphones (or a sound system).

-Twin channel receivers are used by the delegates to listen to either the translated or the floor language. These systems are commonly used throughout countries such as Wales.

-Twin channel systems can also be used for stereo sound applications.

If more than 2 channels are needed then a narrow band infrared system can be installed allowing up to 32 channels. These are used for simultaneous interpretation at international meetings.

Sound Induction Systems manufacture the Sennsis range of portable infrared hearing loop systems. We are Sennheiser main dealers so can supply spare parts including receivers, batteries, ear pads, etc. We also have a large stock of Sennheiser infrared systems for hire. Please contact us for more information.

Have you considered a SENNSIS portable infrared hearing system?

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