Easy listening

Assistive listening has often been misrepresented as only catering for the hard of hearing. That’s far from the case and many of the technologies developed in that market have now found new applications. Here we look at the competing solutions available for assistive listening systems and their relative merits.

The world of assistive listening is awash, like so many other specialist markets, with three letter abbreviations (TLAs). ALSs (assistive listening systems) are made up of ALDs (assistive listening devices) and in some countries these are used as means of complying with the DDA (Disability Discrimination Act) and its equivalents.

So, what exactly is an assistive listening system? The US Government’s access board uses the following definition: “Assistive Listening Systems are intended to augment standard public address and audio systems by providing signals which can be received directly by persons with special receivers of their own hearing aids and which eliminate or filter background noise. The type of assistive listening system appropriate for a particular application depends on the characteristics of the setting, the nature of the programme and the intended audience.”

Increased legislative focus on issues such as disabled access to facilities has forced owners and operators to re-evaluate the systems they have in place and consider upgrades or completely new ALSs. However disability access is only one part of the market. Any environment in which supplementary audio is required is a candidate for a system, whether that’s a factory tour, a museum, a theatre or a school.

Another interesting driver for the adoption of assistive listening systems is a change in attitude towards provision. In the past systems to help the deaf or hard of hearing have been used for just that. No thought was given to offering these same facilities to those without a prescribed hearing aid or normal hearing, who simply want an enhanced experience. However in countries such as Spain, access legislation is written in such a way as to offer equal opportunity to both the hard of hearing and those without supplementary listening requirements. So it is now possible to use a headset with a telecoil which operates in exactly the same way as a hearing aid allowing anyone to hear the programme.

Technology choices

Assistive listening devices are based broadly on three technologies. Induction loops, Infrared and Radio. Depending on who you talk to they each have their advantages and disadvantages and are suited for various applications.

Induction loops are worth a little more explanation due to being a slightly special case in how they operate. The audio signal to be augmented is fed into an induction loop amplifier. This drives a current in a loop or series of loops of cable. The carrying cable generates a magnetic field and it is this induced field that a person’s hearing aid picks up on and returns to an amplified audio signal via a telecoil in the hearing aid. Telecoils can also be fitted to other devices allowing them to pick up the signal from the induction loop.

However in order to be truly effective, it’s vital that induction loops are correctly installed. The single biggest problem that manufacturers of these systems face is the miss-installation of their products leading to poor performance and dissatisfaction from customers and users. Julien Pieters, Managing Director of loop manufacturer Ampetronic said: “What really makes the difference between a good loop and a bad loop system isn’t the equipment, but the design and implementation. That’s why so much of our activities are centred on education. There is an international standard for induction loop performance and it’s pretty demanding. But the reality of the situation is that if your don’t follow it, you might as well not bother plugging in the loop at all.” The company provides a great deal of useful information about induction loop system design and the relevant standards on its web site.

Anthony Smith, MD of competitor Current Thinking concurs, saying “At the end of the day it’s not the integrator’s name that’s on the front of the amplifier, it’s ours. The education we do can be down to something as simple as correct microphone placement. If you don’t get the fundamentals right, the system just will not work.”

The clear advantage of an induction loop is that for a hearing aid user there is no need for additional receiving equipment. This means that system owners have no need to worry about headsets, charging batteries and so forth. It’s also more discrete for the user. There’s no need to announce yourself to a reception desk and say “Excuse me, I’m hard of hearing. Can I have one of your headsets please?”

There are drawbacks however. The initial installation cost can be very high, especially in the case of the more complex array systems. There is also the question of operating multiple loops in proximity. Simple perimeter loops in adjacent rooms can spill over in to each other through walls. The solution is to use a low-spill loop array, which cuts this effect right down, but involves more cable and more powerful equipment. Induction loops are not always the easiest solution for retrofitting to existing sites, but Pieters argues the point: “I wouldn’t always say that retro-fitting an induction loop is particularly difficult. Of course if you need a really complex array and have to take the floor up then that’s an issue, but a simple perimeter loop system is relatively quick and easy to install. Certainly it’s not as simple as putting an IR emitter on the wall, but that’s not the complete picture once you take total cost of ownership and other factors into account.”

FM based systems are used extensively for guided tours, houses of worship, and outdoor applications. They are cost effective, especially in large scale systems, and are not dependant on line of sight - a failing of their IR brethren. They are also simple to install and operate.

However FM does suffer from a number of disadvantages. Firstly, radio signals are not generally constrained by walls, or buildings. This means that FM can suffer the same leakage problems associated with induction coils. It’s therefore unsuited to applications such as the corporate world or other sensitive sites. It is also susceptible to outside interference from other users of the radio spectrum such as FM antennas, cell phones and pagers.

Despite these drawbacks, FM still holds a massive chunk of the assistive listening market, and therefore there is still a large amount of new product development going on. Sennheiser has fully digital tour guide system, the HDE 2020-D, which offers 6 channels over the 862-865 MHz frequency range. John Willett, Sennheiser’s expert on assistive listening systems points out the importance of multiple channels for tour guide applications: “It’s worth noting that there is no distinction here between hard of hearing and translation channels. So, what passes for an Italian translation channel must also be suitable for an Italian hard of hearing person. Not all people with hearing problems speak the same language!”

Williams Sound’s marketing manager Chad Engel revealed the launch of the companies new Whisper tour guide system for the European market, which will operate at 863 MHz. This is a three-channel system. The number of channels that a system operates over can either dictate the number of different tours that can operate in the vicinity simultaneously, or the number of different languages that could be supplied at once.

Telex, is another long-term provider of FM-based solutions. Its SoundMate range operates as a single channel system in the 72-76 MHz range and is popular in the education market.

The new kid on the block, relatively speaking, is infrared. It scores over both FM and induction based systems in a couple of important ways. The first, and arguable the most important is the issue of privacy. IR signals cannot pass through walls, and therefore leak out of meeting rooms or courts. Infrared technology is therefore finding favour in the judicial system and amongst corporate clients who are looking for alternatives to the easily intercepted radio solutions or the potentially expensive to install induction products. Any multi-room application is ideal for infrared again due to it’s lack of spill over. Cinema operators and schools particularly see this benefit.

The second, related benefit is one of security. Radio based systems transmit their audio unencrypted, which means they can potentially be picked up and understood by any receiver. Infrared on the other hand requires the correct unit.

Chad Engel again: “Our latest infrared product for the European market is more convenient to install than ever. The TX90 combines the audio processor and infrared emitter into one unit, meaning less equipment to purchase, less rack space is taken up and installation time is cut. The system is a two-channel one, making it popular in the disabled access market. For example this doesn’t just require a hearing system over one channel, for the partially sighted there’s also a requirement for audio description. With two channels the TX90 can serve both of these demands in one go.”

IR’s greatest strength has also been its weakness. In the past, in order to pick up the audio signal the infrared receiver on the users headset or neck-worn loop has always needed to “see” the radiator on the wall. Listen Technologies Jan Wintersberg describes how dealers would assess a system at a trade show.

“They put on the receiver units and then turn slowly away from the radiator until the signal stops. There has always been a big perception amongst dealers about what infrared can and cannot do, but we are challenging this with our latest products. With our very latest system we have solved this. Up until now, an IR receiver has been an IR transistor and an amplifier behind it. Today, the technology is a microprocessor, a diversity receiver and of course a few secrets. The new receivers allow us to catch every single reflection in the room.”

The other bane of IR systems, and one which is much harder to overcome is light itself. Older systems were highly susceptible to interference from devices such as fluorescent lighting, and whilst this has been overcome with the switch to 2.2 MHz technology and beyond, plasma screens and direct sunlight can still kill off an IR system.

What does it all mean?

Ultimately there is space in the market for all three systems. Each has its relative merits and drawbacks. Whilst those manufacturing one system will say that theirs is the best solution the usual balancing act between cost and feature set applies. What is most telling is that in terms of both IR and radio based technologies all of the major players offer both solutions. Advances in infrared technology are eliminating some of its drawbacks, but it still struggles to compete with radio based solutions on cost in large-scale installations.

Induction loops also retain an important place in the market, especially for the disabled access space. The lack of need for any additional equipment on the part of the user means they will continue to find applications in new markets such as public transport or car parks. Just remember that if you plan on getting involved in installing loop systems your first port of call should be proper training from the manufacturer.

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