EAV Pro Audio have recently set up a 'Hearing assisted audio' section on our website that consists of hearing loop systems and Infrared systems. This little guide helps you understand what these things are, how should have one, how they work and techniques for getting the best out of your hearing assisted audio systems. Our sister company, Acoustic Arrangements, have been installing Loop and Infrared systems into churches for over 15 years, if you have questions regarding them, please give us a call on 0845 125 9409
TYPES OF HEARING SYSTEMS
What are induction loop and infrared systems?
Hard-of-hearing people find it difficult to hear in larger venues because of poor room acoustics. The problem is made worse by the distance that sound has to travel before it reaches the audience, background noise and competing sounds.
Induction loops and infrared systems reduce background noise so that sound can be heard more clearly.
How do they work?
Induction loops and infrared systems replace the sound path between the sound source and the hard-of-hearing person with either an inductive (magnetic) or infrared signal that is not affected by acoustics or other sounds.
The hard-of-hearing person uses a receiver that converts the signal back to sound. With loop systems, this is usually their own hearing aid (only those with a ‘T’ position). Infrared systems use special receivers to convert the signal back to sound. Both systems enable users to hear from anywhere covered by the system. The sound that people hear without a receiver is unaffected.
What is an induction loop?
An induction loop is a cable that encloses the audience area. It is connected to a loop amplifier that gets its signal from a microphone placed in front of the person speaking or via a direct connection from a sound system, or other sound source. The resulting electric current in the loop produces a magnetic field corresponding to the speaker’s voice. Anyone within the area of the loop who is wearing a hearing aid switched to the 'T' setting, or a loop listening aid, can pick up this field. Users may need to adjust their own hearing aids for volume.
The loop wire usually runs around the edges of a room so that it serves the entire audience area. Sometimes, however, it only encloses a particular seating area. It can also be routed over doors and arches. This doesn’t affect how the loop works.
Loops consist of ordinary insulated cable, but the gauge must be chosen with care. The cable is normally run around the edges of the room – usually a single turn is used, but some systems may need two or more turns of cable to generate sufficient magnetic field or to match the amplifier’s characteristics.
Tricky loop design situations
External factors may affect how well a loop works. These could be such things as metal work, pillars and pipes and high ambient RFI (see below). Think about these when you begin to plan – sometimes they may influence whether or not you install a loop at all. Some problems however may not arise until after the loop has been installed.
Interference from other circuits (RFI)
Even if the loop itself works properly, hearing aid users may hear magnetic interference from electrical equipment and wiring, such as fluorescent lights, light dimming systems or power cables. This interference is picked up directly by their hearing aids. You can usually identify sources of interference using a portable field strength meter, hearing aid or loop listener. If it can’t be prevented or reduced, assess the interference to see if it will be acceptable to people using the loop. Interference from other electrical equipment is a common reason for people not getting the intended benefit from a loop system – so pay close attention to this point.
Loop systems are designed for users within the area of the loop, but there is always some overspill, as walls, ceilings and floors do not block magnetic fields. This means hearing aid users outside the looped room may be able to overhear conversations if their hearing aids are switched to 'T'. The magnetic field may also overspill into adjoining rooms and rooms directly above and below. You should think carefully about this if you are fitting more than one loop area. If this could be a problem, you could consider an infrared system instead.
Interference to other circuits
In some circumstances, an induction loop may cause interference in other parts of a sound system, instrument pick-ups or video systems. This can happen if the loop cable runs close to other signal cables that are especially vulnerable to this kind of interference. Carefully routing the cables may prevent this problem, but ground loop isolation is sometimes required and can be expensive.
Metal in buildings
This can have an unpredictable effect on loop systems. The loop may produce a weaker inductive signal than expected if the metalwork in the area of the loop is substantial, and the signal strength may vary from seat to seat in the listening area.
Ideally, you should use a field strength meter with headphone output to check the system. This lets you check both magnetic field strength and quality of signal. You should test the loop regularly and adjust as necessary – how often will depend on your venue.
What is an infrared system?
Infrared systems can provide high-quality sound and are available in stereo (or dual mono) versions. They use invisible infrared light to carry sound to portable receivers. The complete system consists of infrared 'radiators', that gets its signal from a microphone placed in front of the person speaking or via a direct connection from a sound system, or other sound source, personal IR receivers are then used for the user. Radiators cast infrared light over the listening area, rather like floodlights. You may need one or more infrared radiators, depending on the size of the venue. The quality of sound received by the user is of a much higher standard than that of induction loop systems.
Anyone using the receiver can sit anywhere in the area covered by the radiators. The infrared light produced by the radiators usually reflects off walls and surfaces in and around the coverage area. So sound should be received anywhere in the covered area, but some wall coverings absorb infrared light, meaning that the receivers will only work when they are pointed towards the radiators.
The most widely-used kind of infrared receiver is a ‘stethoset’ which is worn without a hearing aid but you can also get a ‘neck loop’ receiver that can be used by someone wearing a hearing aid, set to 'T'.
Most venues keep both types of receiver and keep the batteries in the receivers fully charged. The ear tips of a stethoset must be cleaned or replaced after use.
Infrared systems are not prone to interference unless the receivers are in direct sunlight. The radiators do not transmit outside the room they are used in, so several systems can be used at the same time in rooms next to each other. For this reason, they are also suitable for confidential meetings. Infrared systems eliminates problems encountered by use of induction loops on instruments, audio signal cables, video and VGA cables.
How much do induction loop and infrared systems cost?
A DIY loop in a small meeting room can cost a few hundred pounds. A professionally installed loop in a big venue can cost several thousand pounds. Infrared systems tend to be more expensive than loops because you need a stock of receivers.
Some organizations install cheaper systems designed for domestic use in their smaller rooms, but check first that this sort of system is suitable and that it meets health and safety requirements.
Helping your customers get the most from your system
The quality of the signal your system produces can only be as good as the signal it receives. Loop and infrared systems do not improve signal quality – they simply reproduce what is fed into them. It is easy to get a clear signal when someone speaks directly into a microphone. The further the sound has to travel to reach the microphone, the poorer the sound quality, particularly if you have poor room acoustics or background noise. Place the microphone as close as possible to the person speaking. This is fairly easy if speakers remain in the same spot. It becomes more difficult when speakers sit in different positions or move around. If this is the case, you will need to choose the correct type of microphone and plan where you place it.
Operating the system
You can leave some infrared or induction loop systems on all the time. Otherwise you will need to turn your system on each time. Even with lots of microphones, or other audio sources such as tape or CD recorders, the controls on the mixing console are usually set up and fixed. You will need someone to operate the mixing console if the system is part of a larger sound system.
What is the Disability Discrimination Act 1995 (DDA)?
The DDA aims to stop discrimination against disabled people, including deaf and hard of hearing people, in the workplace, in education and when accessing goods and services. Goods and service providers include theatres, cinemas, places of worship, conference halls, banks, courts and tribunals, supermarkets, airports, shopping centers and bus and train stations.
The Act says that service providers may not discriminate against a deaf or hard of hearing person by refusing to provide a service or offering a service of a lower standard or on less favorable terms, on the grounds of their hearing loss. Service providers must make reasonable provision and adjustments to the way in which they provide goods or services to enable deaf and hard of hearing people access to them.
If it is not reasonable to provide a permanent loop or infrared system, then the service provider should provide a temporary system.
If you already provide an induction loop or infrared system, you are required by law to make sure that the system is properly maintained and that staff are aware of it and know how to use it. This applies to temporary and permanent systems.
You must also make sure that additional equipment, like neck loop receivers or loop listeners, are maintained and tested, and that you have a reasonable number. You should make sure that you display signs telling customers that a loop or infrared system is available.