Science Interviews


Sun, 12th Jun 2011

Better Hearing for Dummies

Professor Ray Meddis, University of Essex

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Jane -  Hearing aids work on the general principle that if you are finding it hard to hear something you simply turn the volume up.  Fine if you are talking to one person in a quiet room, but if you are in a noisy environment then everything is amplified.  Now unique computer modelling techniques, combined with new ways of carrying out hearing tests, are revolutionising the way that hearing loss and impairment is diagnosed and treated.  Professor Ray Meddis is leading the work at the University of Essex.  

Ray -  Hearing consists of a number of stages between the sound arriving at the ear and then the signal going up to the brain. The computer model tries to represent each one of these stages separately. The test that we use involved two measurements, one concerns tuning and the other one concerns compression.  Tuning refers to the situation where you can hear one sound and tune out background sounds.  Itís a bit like a radio where you can tune into one radio station, but you donít want interference from another station.  Now with normal hearing this tuning takes place naturally so one of our tests focuses on that particular problem.  Compression is concerned with how intrusive other sounds are when they become louder. So normally we can tune out another sound if it is quiet, but as it increases in intensity then we have more difficulty in tuning it out.  A person with hearing loss often has a particular difficulty in tuning out irrelevant sounds and so our compression measure is particularly concerned with increasing the intensity of the sound and then noticing how that comes to make it difficult to listen to a particular vocal sound.                               

Behind the ear hearing aidJane -   Strange as it may seem, it was the art of dressmaking that inspired Ray and his team to take this tailor-made approach to the diagnosis and treatment of hearing impairment.

Ray -   When generating a computer model for a patient with hearing loss, we always start off with a normal model and we try and make a single adjustment which refers to the particular pathology which we feel is causing the problem for that particular patient. When you have a dress made the tailor measures your body size then changes the shape of the dummy to represent your body size and then cuts and sews the clothing so that it fits the dummy.  The reasonable expectation is that when the customer comes back the clothing will fit the customer perfectly.  Now we believed that we could do the same thing with hearing impairment.  We already have a model of normal hearing, so by making certain adjustments we could make the dummy simulate impaired hearing and the idea was we could then use that dummy to fit the hearing aid and we would adjust the hearing aid so that we got the best possible output from the impaired hearing dummy.  Our hope is that we will be able to use the hearing dummy to make these adjustments before the hearing aid is supplied to the patient.  In other words the hearing aid should be fitted to the dummy just like a dress would be fitted to a tailors dummy and then when the patient comes back, ideally, the aid should be perfectly suited to their particular needs.

Jane -   Supported by the Engineering and Physical Sciences Research Council, this cutting-edge work has also led to a prototype design for a new type of hearing aid.

Ray -   Because our primary interest was in developing computer models we came to realise that hearing aids respond differently to sounds compared to a normal hearing individual.  So it seemed to us that we could build a hearing aid that simulated normal human hearing so it compressed the sound in the same way, tuned the sound in the same way and dealt with variations in level in the same way. We have designed a new type of hearing aid which uses something called instantaneous compression.  Currently in hearing aids sound is compressed, but it takes a little while for the compressor to respond to the sound levels and this gives rise to some complications.  But by simulating normal human hearing weíve been able to produce instantaneous compression without the distortion which everybody used to believe was an unavoidable accompaniment of instantaneous compression.

Jane -   So a number of aspects of this research are cutting-edge.

Ray -   The research is a world first in a number of respects.  First of all this will be the first model to represent a number of different kinds of hearing impairment.    It is also the first attempt anybody has made to go through the complete cycle that is measuring the hearing loss, designing the hearing dummy, adjusting the hearing aid using the hearing dummy and then modifying the hearing aid to suit the patient.  

Jane -   The new approach has simplified the complicated laboratory testing process, significantly cutting down on the time it takes and the number of trials involved, along with the level of expertise required.   Within four years we could see this system of testing in widespread use, along with the new type of hearing aid.


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I'm not quite sure what all is new.
As I understand it, the hearing aids consist of an electronic portion, and an ear portion.

The ear portion is fitted to each individual's ear.  I always thought they essentially made a cast of the ear canal, although I suppose one wouldn't want someone pouring wax or plaster into one's ear.  One could make an electronic "cast" of the ear pretty easily.

The electronics have a lot that can be played with.  For example, if certain tones are lost, those tones can either be amplified more, or perhaps have the whole sound spectrum compressed to utilize the tones that can actually be heard.

One thing that I think is lacking in the current generation of hearing aids is wireless and bluetooth technology.

When in a crowded restaurant, the hearing aid wearer should be able to had their spouse or companion a microphone to selectively amplify that person's voice.  Likewise, in a car, the spouse should have the microphone, to amplify their voice while lowering road noise.  Of course, allow a half dozen transmitter clones for groups, and perhaps even allow multiple hearing aid wearers to sync to the same devices (with eavesdropping security, of course).  A TV should be able to transmit directly to the hearing aid.

As technology improves, perhaps they will add voice recognition software and better background noise filters. CliffordK, Tue, 14th Jun 2011

Some of the aids now incorporate basic wireless technology so when you change the program on one it changes the other ear to same program automatically. You can also have them configured to follow volume changes on one on the other - but since I might want to adjust them independently if my real ear has gone extra quiet or something I don't have the volumes linked. techmind, Sat, 25th Jun 2011

I have had the experience of a number of elderly relatives who have developed severe hearing problems. I would observe that the biggest problem in improving their hearing has little to do with the electronics involved but is how such aids are marketed - both from a technical and commercial point of view. So much can be done with technology but very little of this is effective in helping the average elderly person suffering hearing loss.

1. There are quite a few companies selling aids to elderly people. Some of these cost over £1000. Much of the selling of such devices is exploitative in the extreme and aimed at an easy target for aggressive sales people.

2. They incorporate (at best) a preset graphic equaliser and a volume control that is awkward to adjust and can frequently result in howling feedback when set too loud.

3. The designs try to be unobtrusive (i.e. small and fit in and behind the ear). Most elderly people are not so self conscious about this add would prefer something that worked better. The feedback problem results from the output sound being near the microphone and having good sound isolation between them. The smallness results in needing to use very small (but expensive) batteries that don't last long and a fiddly to change.

4. This is all quite ironic when young people frequntly walk around with very high quality earphones in plugged into an Ipod (or other HiFi system) and are quite happy with a couple of wires to a small box where they have full control over the features and sizeable rechargable batteries that can run for long periods. I recently noticed an advert for a hearing aid (Japanese company) based on a more sensible system like this. They are also harder to lose!

5. The array of noise cancelling features that can be applied and modified with software upgrades to such a DSP based system is immense and would not involve changes to the hardware and difficulties for the users.

In short, my experience of what happens in practice in this market leaves me very cynical about many of the products that emerge. Many years ago I can remember a couple of my elderly aunts who had deaf-aids which included a black-box (the size of a large, modern mobile phone) worn on their chests. These were very simple amplifiers but systems that they could use easily into their late 90's in both cases, and they worked! Recently I have known many old people who cannot use their hearing aids (or at least not use them well) and one or two that simply won't use them because of this. Concentrating on technological improvements is great, but someone ought to do proper and realistic market research for the majority of their targetted customers. graham.d, Mon, 27th Jun 2011

I agree with syncing devices so conversations can be continue within a large group.  In my understanding of large groups of people, there tends to be a specific region of frequency ranges.  You can possibly tune into some and get what you need.  As far as Algoryhmic pre-selection.  It is subjective.

It is often the case that medium to large groups of people create harmonious dissonance. To describe it would be to say, I can hear everyone but no one

Having not studied it in great detail, I know through simple eq work I can find what I want to hear.  Again I am being subjective as a musician.

What we hear as sound is only part of this entire spectrum of energy.

LongWave worked very well in it's time.

I agree on the idea of reverse technology (where the reciever is on your chest)

but it doesnt need to be the battery pack as well.  Surely  a good quality omni mic (which is almost invisible, even movies have made them into jewelery.  So, a tie pin or a broach or even a nipple clamp could be your near voice receiver.  All it needs is enough power to send it's detail for say 7 hours to the mobile phone in your pocket and transmit it back to your ear, or even better! your ear directly?

It might be the case that the tie pin / broach / watch / glasses / nipple peircing will have some form of transmitter to your ear piece.  Maybe via Bluetooth or any number of closed transmission options.

there is now technology where you can leave your Tiepin (mic) and earpiece (head stuff) on a platter that will charge them so easy, no thinking of where do I plug this in.

It might be the case that the tie pin / broach / watch / glasses / nipple peircing will have some form of transmitter to your ear piece.  Maybe via Bluetooth or any number of closed transmission options.

You could be in a situation where you can control what you want to hear via your mobile phone.  You may even have eq profiles that work with certain situations, and certain people. 

You could to the ultimate.  You could analyse someones voice and tune them out from your hearing aid.

So you never have to hear them again.


Nothing I have said is impossible, just needs a bit if desire.



FULKRAM, Fri, 1st Jul 2011

From my (personal) experience, the "problem" is rarely the limitations of the hardware, but its complexity and the time taken to set it up properly. One NHS audiologist admitted that they normally only set up the basic features because that's all they have time for. Although when you pay extra to go private you are likely to get a newer aid with more technical capability for most people this probably isn't required... but what the huge fee does buy you is plenty of time with an audiologist.
Even the regular aids (which I understand the NHS buys in bulk for under £100 each) would probably take a full working day with an audiologist, in several sittings, to really set up optimally. Bear in mind the patients' patience, as well as that of the audi.

Of course, although some of the more sophisticated processing can be beneficial, it often also has its drawbacks:
-Feedback cancellation algorithms often cause "entrainment" artifacts - 'ringing' following impulsive sounds like tapping on a computer keyboard, pulsating in the presence of pure tones such as electronic beeps (pelican crossings, coffee machines) or music (especially organ music), and generally odd behaviour in the kitchen when a washing machine is in cycle(!)
-'Directional' performance attempts to use 2 or 3 microphones to enhance sound from the front relative to general ambience... which can help but also messes up the frequency-response (losing low frequencies and/or having to enhance them - which is then critically dependent on the 2 or 3 microphones remaining perfectly matched over the life of the aid)
-Automatic switching between programs may be beneficial - but I find completely disorientating.

Aids which go (intermittently) quiet for anything from a few days to a few hours BEFORE the low-battery indicator beeps sound don't help. In colder weather, low-battery symptoms frequently are first noticed when going outside into the cold (batteries being chemical devices...)
Tiny (eg 1mm bore) tubes can easily get plugged with earwax which kills the sound alomost completely and need to be manually poked to unblock...

I'm young(ish) and technically very-on-the-ball. Hearing aids work for me, but they're not perfect and still a bit of a faff. For someone not technically astute, with failing eyesight and failing sensitivity in the fingers, they're far form ideal.

My aids have a tendency to exhibit 'clipping' distortion ('buzzing'/'rattling') in the presence of bass-beats or certain conditions of piped music (a problem in some pubs), even when the overall volume level is not especially high. I would have thought the software to configure the aids should avoid combinations of settings which distort, but this doesn't necessarily seem to be the case. Again, I can analyse what's going on, find some way to reproduce the problem 'on demand' (thumping mugs on tables, or playing test-tones on my mobile phone(!)...), then go back to the audiologist to try to fix it. By far the majority of hearing aid users simply won't be able to do that.
techmind, Mon, 4th Jul 2011

What I would really like to buy is a mobile phone into which I could plug a microphone and ear piece to use as a deaf aid.
my £30.00 mobile phone all ready incorporates a FM radio and camera so the extra cost to incorporate this would be trivial.
I have some hearing loss but baulk at the idea of paying £1000.00 for £20.00 pounds worth of electronics  syhprum, Wed, 11th Jan 2012

You can get bluetooth microphone/earpieces that work with many cell phones.  I just don't use mine enough to make it worthwhile.  Some cell phones also have corded earpieces with a microphone that hangs down somewhere in front of the mouth.

I assume you could adapt your best sound-cancelling bose headphones to work with the cell phones with the plug-in earphones.

At work, a few people insisted on ordinary analog cordless phones because they all supported rather inexpensive telephone headsets.  The ATT Digtital phones apparently had a headset option that wasn't bad, but was about 5x as expensive. CliffordK, Wed, 11th Jan 2012

I have been looking at mini FM transmitters that could be used in conjunction with the FM radio in the mobile phone, one is available for £12.00 that has a microphone but most just accept an input from a MP3 player the only problem is it works on 114-116 MHZ just above the broadcast band but maybe some adjustment could be made. syhprum, Wed, 11th Jan 2012

Bluetooth is the way to go.
However, if the goal is FM radio, the cell phone that I had that supported FM used the earphone wire as an antenna.  It technically would work without it, but it didn't like it.  CliffordK, Wed, 11th Jan 2012

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