Hearing loops....how do they work?!

[steve208]

I have seen these in shops and presume they are for deaf people but how on earth do they work and if they make sound then surely they are for people who can hear a bit????

[Buenchico]

Hearing loop systems can cover a wide area (e.g. so that the same signal can received throughout the auditorium of a theatre) or the can be localised. (e.g. so that two people making enquiries at adjacent windows at a railway booking office can each only hear the individual railway employee who is serving at that window).

The systems work by creating an 'induction loop' of magnetic energy which carries the signal picked up by microphones on the stage of the theatre (or in front of each assistant at the railway booking office). They are for the benefit of hearing aid users who use aids fitted with 'T-coils' (which receive the signal).

A person who uses the appropriate type of hearing aid operates a switch (to the 'T' position) on their hearing aid. Instead of operating in the normal way (where a small microphone in the aid picks up sounds) the hearing aid now uses the T-coil to pick up the signal from the loop.

Your confusion seems to arise, partly, from the assumption that everyone who is registered as 'deaf' has a total hearing loss. For many (possibly most) 'deaf' people, this isn't the case. (i.e. they have a severe hearing impairment but they retain limited hearing which can be assisted by the use of a hearing aid).

Chris

[steve208]

thanks you very much for your detailed reply but im still confused...so the loop sends a signal to the hearing aid and it amplifies the voice of the shop assistant for example?

[ACB312]

Buenchico's answer is (as usual) perfectly correct and what you have to understand is the difference between audible sounds (compression and rarefaction of air) and electromagnetic radiation. Hearing aids can be set (by switch) to pick up audible sounds and amplify them accordingly (with various audio filters) for a hearing impaired person. Sometimes, the audio level from a person behind a screen is too low for the aid to pick up, so a local microphone picks up their speech, amplifies it and instead of sending it to a loudspeaker it goes to a loop of wire which acts like the coil of a loudspeaker and emits an electromagnetic field in sympathy with the voice input of the speaker which can be picked up with the hearing aid in the T position. This is, of course, inaudible to normal human hearing. Going back to your question - the loops do not make sound - they make electromagnetic radiation.Hope this helps.

[Buenchico]

If you see a 'hearing loop' sign in a shop, there's probably not a single loop (like there is a a theatre) but a series of local loops around each counter. Each counter position is equipped with a microphone. (These are usually extremely small and discrete. I used to run a railway station and I've known booking office staff serve at the same window, every day, for over two years before they've noticed the tiny microphone in front of them!).

Each microphone feeds into a local loop so that the assistant's voice is 'broadcast' by a magnetic signal around the counter at which they're serving. The customer's hearing aid (set to the 'T' position) picks up this 'broadcast' and converts it back to sound, through the earpiece.

Any clearer now?

Chris