Assistive Listening Systems - replace this text

Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Aenean tempor, enim sed consequat porta, tortor dui egestas nisi, eu hendrerit purus justo nec sem. Maecenas tincidunt lobortis erat. Donec ut ligula. Vestibulum lacinia luctus lectus. Maecenas id felis sed mauris lobortis consequat. Suspendisse ligula. Fusce at nisl sed massa ultrices aliquam. Pellentesque ornare, leo eget pellentesque vestibulum, enim massa congue urna, sed tristique est purus ornare ante. Suspendisse potenti. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Praesent urna ligula, dictum vel, lacinia eu, auctor in, nisl. Suspendisse potenti. Fusce sit amet erat sed odio lacinia convallis. Cras pellentesque leo sit amet est eleifend pretium. Praesent congue mattis enim. Vestibulum interdum nunc quis est. Nunc diam orci, tincidunt nec, tincidunt ut, dictum iaculis, eros.

Maecenas eleifend purus et ligula. Aliquam facilisis velit ut libero. Suspendisse eleifend. Duis vel arcu. Sed at ipsum nec leo gravida rhoncus. Nam in orci. Nam porta libero sed neque. Vestibulum quis ipsum. Vivamus posuere. Duis vestibulum rhoncus lacus. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras varius purus ut urna. Fusce sit amet urna.

Digital hearing aids are not a panacea

In many environments, even the best digital hearing aid is not enough for the hard of hearing to understand what is being said.

The hard of hearing find it very difficult to separate the background noise from the wanted signal. Digital filtering techniques and directional' steerable microphone technology can help, but fundamentally, the noise and wanted signal will contain the same frequencies and may also have the apparent same position of origin.

To overcome these issues the intelligible sound needs to be somehow physically isolated from the noise sources. This is easily achieved with recorded material, but for live speech it is a big problem.

In a crowded noisy bar we will get close to the person we want to talk to and probably speak directly into their ear to be heard above the background ambient. Assistive listening systems employ the same strategy. A microphone is positioned as close to the person speaking as possible meaning only their voice is picked up. The output is processed, amplified and delivered directly into the listener's ear.

There are several competing audio Assistive listening technologies- Induction Loops, Infrared Systems, FM Systems and Personal FM (wireless systems)

'Induction loop systems are the preferred assistive listening technology of the hard of hearing.They are the easiest to manage in a facility and over the lifetime of the system represent the lowest cost solution.'

At the first international conference on Loops and T-coils held in Switzerland Sept 2009, 98% of the delegates voted in favour for a motion in support of T-coils and induction loops.

The following is an extract from the conference courtesy of the European Federation for the Hard of Hearing,

An audio frequency induction loop system (AFILS) is an inexpensive, efficient and universal system to enable people wearing hearing aids or cochlear implants to hear in public situations.

We recommend that:

1) hearing aid manufacturers, manufacturers of cochlear implants, physicians, audiologists and hearing instrument specialists shall communicate the benefits of hearing aid / cochlear implant telecoil receivers for phone listening and assistive listening and educate people who are hard of hearing accordingly.

2) venues and service points where sound is broadcast shall offer assistive listening, such as induction loop systems designed to the IEC 60118-4:2006 standard, that broadcast sound directly to hearing aids and cochlear implants, enabling them to serve as customized, wireless loudspeakers (without the need for extra equipment).

For more information visit www.efhoh.org

There are several competing audio Assistive listening technologies, Induction Loops, Infrared, FM and Personal FM (wireless systems).

The table provides a summary of how they compare.

How they Compare

In this example, the hard of hearing person is using an induction loop system to listen to the TV.

The system comprises an induction loop amplifier connected to a loop of cable placed around the perimeter of the room.

The audio output of the TV is connected to the input of the amplifier which in turn drives a current around the loop. The current is modulated by the audio input and therefore carries the audio signal. As the current flows round the loop, it sets up a magnetic field. This magnetic field which now contains the audio, induces a current into the pick up coil, T-coil of the hearing aid. The induced current is processed by the hearing aid, tonally corrected for the persons individual hearing loss, amplified and fed directly into the ear through the hearing aid apeaker.

' It is like putting your ear up against the speaker.'

All induction loop systems work in the same way. The loop configuration may be more complex, figure -8, Super 8^TM SuperLoop^TM etc and the input signal feed maybe from a microphone, audio mixing desk, PA or other source, but the principles are still the same. An electric current carrying the audio signal flows through a cable setting up a magnetic field which induces another current to flow in the T-coil of the hearing aid. This current is processed by the hearing aid and fed into the ear through a speaker.

NOTE

Just because an induction Loop system complies to the performance standard IEC60118-4:2006, it does not necessarily mean than it provides any benefit to the users. The audio input must be good quality, and as far as possible, free from background noise. For live speech and music, the easiest way to achieve this is to use radio microphones, which can be worn by the speaker.